refactor(windows-host): §2.5 step 1 — delete the dead/write-only monitor-lifecycle code

Removes the cruft the §2.5 ownership-model rewrite would otherwise carry forward, and corrects a
false invariant the docs described:

  * CURRENT_MON_GEN (sudovda) — the "current monitor generation" global was WRITE-ONLY. It was
    stored on every mgr_acquire (both backends) but its only reader, idd_push's `my_gen`, was set
    and NEVER read. The "session capturer re-checks the monitor gen each frame and bails on a
    reconnect" behaviour the doc describes was never wired — per-frame staleness is the SEPARATE
    ring FrameToken.generation / IDD_GENERATION mechanism (which works and is untouched). So the
    monitor-gen-via-WinCaptureTarget carry the design proposed is unnecessary. Deleted the static,
    its stores in both backends, the pf_vdisplay import, and idd_push's dead `my_gen` field/read.
    (MON_GEN — the lease-generation counter behind the stale-lease no-op — is REAL and kept.)

  * IDD_PERSIST + open_or_reuse + IddReuseHandle (idd_push) — a persistent-capturer reuse path
    from an early prototype, defined but with ZERO callers across the crate. Deleted, plus the now
    -orphaned `use std::sync::Mutex` and the now-dead `set_client_10bit` setter.

Windows-only; grep confirms no remaining references to any deleted symbol. Box build to follow.
First of the incremental §2.5 steps (user-approved OnceLock VirtualDisplayManager design).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

crates/punktfunk-host/src/capture/windows/idd_push.rs

@@ -15,7 +15,6 @@ use super::{CapturedFrame, Capturer, FramePayload, PixelFormat};
 use anyhow::{bail, Context, Result};
 use pf_vdisplay_proto::frame;
 use std::sync::atomic::{AtomicU32, AtomicU64, Ordering};
-use std::sync::Mutex;
 use std::time::{Duration, Instant, SystemTime, UNIX_EPOCH};
 use windows::core::{w, Interface, HSTRING};
 use windows::Win32::Foundation::{CloseHandle, HANDLE, INVALID_HANDLE_VALUE, LUID};
@@ -152,111 +151,11 @@ pub struct IddPushCapturer {
     last_seq: u64,
     last_present: Option<(ID3D11Texture2D, PixelFormat)>,
     status_logged: bool,
-    /// The monitor generation this capturer was opened for. When the active monitor gen changes (a
-    /// reconnect preempted + recreated the monitor), `next_frame` bails immediately so this session
-    /// releases its NVENC encoder instead of lingering on the dead ring's 20s deadline.
-    my_gen: u64,
     _keepalive: Box<dyn Send>,
 }
 // COM objects used only from the owning (encode) thread.
 unsafe impl Send for IddPushCapturer {}
 
-/// The persistent IDD-push capturer, kept alive for the host lifetime and SHARED across client
-/// sessions. The driver's per-session monitor TEARDOWN→RECREATE path is unstable (on session 2 the
-/// target-id resolves to 0, `IddCxSwapChainSetDevice` fails `0x80070057`, then an access violation),
-/// while the FIRST-session path is solid. So we create the monitor + ring + swap-chain ONCE and hand
-/// every later session a thin handle delegating to this one. The persistent capturer holds a monitor
-/// lease for the host lifetime, so `VirtualDisplay::create` always JOINs the same live monitor (same
-/// target id) and the reuse match always hits — no recreate, no driver crash. Prototype scope:
-/// single-client, single-mode (a different mode would need a recreate, the unstable path).
-static IDD_PERSIST: Mutex<Option<IddPushCapturer>> = Mutex::new(None);
-
-/// Open the IDD-push capturer, reusing the persistent one across sessions (see [`IDD_PERSIST`]).
-pub fn open_or_reuse(
-    target: WinCaptureTarget,
-    preferred: Option<(u32, u32, u32)>,
-    client_10bit: bool,
-    keepalive: Box<dyn Send>,
-) -> Result<Box<dyn Capturer>> {
-    let (w, h, _) =
-        preferred.context("IDD push needs the negotiated mode (WxH) to size the ring")?;
-    let mut slot = IDD_PERSIST.lock().unwrap();
-    let reuse = matches!(slot.as_ref(), Some(c) if c.target_id == target.target_id && c.width == w && c.height == h);
-    match slot.as_mut() {
-        Some(c) if reuse => {
-            // Reuse: the persistent capturer already owns the monitor + ring + driver attach. Drop the
-            // new per-session monitor lease (the persistent capturer's lease keeps the monitor live).
-            // The ring tracks the display, not the client; only the client's 10-bit cap can differ.
-            drop(keepalive);
-            c.set_client_10bit(client_10bit);
-            tracing::info!(
-                target_id = target.target_id,
-                client_10bit,
-                "IDD push: reusing the persistent capturer (no monitor/ring recreate)"
-            );
-        }
-        Some(c) => bail!(
-            "IDD-push persistent capturer is {}x{} target {}, this session wants {}x{} target {} — a \
-             mode/target change needs a recreate (the driver's recreate path is unstable); not \
-             supported in the persistent prototype",
-            c.width,
-            c.height,
-            c.target_id,
-            w,
-            h,
-            target.target_id
-        ),
-        None => {
-            tracing::info!(
-                target_id = target.target_id,
-                client_10bit,
-                "IDD push: creating the persistent capturer (first session)"
-            );
-            // (dead persistent path) open() now returns the keepalive on failure; this path has no
-            // fallback, so discard it on error.
-            *slot = Some(
-                IddPushCapturer::open(target, preferred, client_10bit, keepalive)
-                    .map_err(|(e, _keepalive)| e)?,
-            );
-        }
-    }
-    Ok(Box::new(IddReuseHandle))
-}
-
-/// Thin per-session handle: every method delegates to the single persistent [`IddPushCapturer`].
-/// Dropping it (session end) does NOT tear down the ring/monitor — that's the whole point.
-struct IddReuseHandle;
-impl Capturer for IddReuseHandle {
-    fn next_frame(&mut self) -> Result<CapturedFrame> {
-        IDD_PERSIST
-            .lock()
-            .unwrap()
-            .as_mut()
-            .context("IDD-push persistent capturer missing")?
-            .next_frame()
-    }
-    fn try_latest(&mut self) -> Result<Option<CapturedFrame>> {
-        IDD_PERSIST
-            .lock()
-            .unwrap()
-            .as_mut()
-            .context("IDD-push persistent capturer missing")?
-            .try_latest()
-    }
-    fn set_active(&self, active: bool) {
-        if let Some(c) = IDD_PERSIST.lock().unwrap().as_ref() {
-            c.set_active(active);
-        }
-    }
-    fn hdr_meta(&self) -> Option<punktfunk_core::quic::HdrMeta> {
-        IDD_PERSIST
-            .lock()
-            .unwrap()
-            .as_ref()
-            .and_then(|c| c.hdr_meta())
-    }
-}
-
 /// Build a permissive (Everyone:GenericAll) `SECURITY_ATTRIBUTES` so the restricted WUDFHost driver
 /// can OPEN the host-created objects — the same `D:(A;;GA;;;WD)` SDDL the gamepad shared section uses.
 /// The returned `psd` backing must outlive `sa`; both are dropped when the process exits.
@@ -521,7 +420,6 @@ impl IddPushCapturer {
                 last_seq: 0,
                 last_present: None,
                 status_logged: false,
-                my_gen: crate::vdisplay::sudovda::CURRENT_MON_GEN.load(Ordering::Relaxed),
                 // Placeholder; `open()` attaches the real keepalive on success, so a FAILED open can hand
                 // it back to the caller for the DDA fallback (audit §5.1).
                 _keepalive: Box::new(()),
@@ -662,12 +560,6 @@ impl IddPushCapturer {
         }
     }
 
-    /// Update the client's 10-bit capability (the reuse path). Only affects whether a fresh `open`
-    /// proactively enables advanced color; the per-frame conversion follows the display, not the client.
-    fn set_client_10bit(&mut self, client_10bit: bool) {
-        self.client_10bit = client_10bit;
-    }
-
     /// Recreate the ring at the format for `new_display_hdr` (the user flipped "Use HDR"). Bumps the
     /// generation so the driver re-attaches ([`is_stale`]) to the new-format textures; clears the
     /// header's `latest` so we don't consume a stale slot from the old ring; drops the conversion

crates/punktfunk-host/src/vdisplay/windows/pf_vdisplay.rs

@@ -38,9 +38,9 @@ use pf_vdisplay_proto::control;
 
 use super::{Mode, VirtualDisplay, VirtualOutput};
 // Backend-NEUTRAL CCD/DXGI helpers reused from the SudoVDA backend (a pf-vdisplay monitor's target_id
-// is a real OS target id, so these operate identically). The shared MON_GEN/CURRENT_MON_GEN generation
-// counter is reused too, so the IDD-push stale-ring bail works regardless of which backend is active.
-use super::sudovda::{CURRENT_MON_GEN, MON_GEN};
+// is a real OS target id, so these operate identically). The shared MON_GEN lease-generation counter is
+// reused too, so a stale preempted lease can't tear down the live monitor regardless of which backend is active.
+use super::sudovda::MON_GEN;
 use crate::win_adapter::resolve_render_adapter_luid;
 use crate::win_display::{
     isolate_displays_ccd, resolve_gdi_name, restore_displays_ccd, set_active_mode, SavedConfig,
@@ -554,7 +554,6 @@ fn mgr_acquire(mode: Mode) -> Result<VirtualOutput> {
         let pm = Some((mon.mode.width, mon.mode.height, mon.mode.refresh_hz));
         let target = mon.target();
         let gen = mon.gen;
-        CURRENT_MON_GEN.store(gen, Ordering::Relaxed);
         return Ok(VirtualOutput {
             node_id: 0,
             preferred_mode: pm,
@@ -581,7 +580,6 @@ fn mgr_acquire(mode: Mode) -> Result<VirtualOutput> {
     let pm = Some((mon.mode.width, mon.mode.height, mon.mode.refresh_hz));
     let target = mon.target();
     let gen = mon.gen;
-    CURRENT_MON_GEN.store(gen, Ordering::Relaxed);
     g.state = MgrState::Active { mon, refs: 1 };
     Ok(VirtualOutput {
         node_id: 0,

crates/punktfunk-host/src/vdisplay/windows/sudovda.rs

@@ -19,12 +19,6 @@ use std::sync::{Arc, Mutex, Once};
 // backends keeps the idd_push stale-ring bail working regardless of which backend is active).
 pub(crate) static MON_GEN: AtomicU64 = AtomicU64::new(1);
 
-/// The gen of the CURRENTLY-active monitor. A session capturer captures this at open and re-checks it
-/// each frame; when it changes (a reconnect preempted + recreated the monitor), the old session bails
-/// IMMEDIATELY instead of lingering on the dead ring's 20s frame deadline — which would otherwise hold
-/// its NVENC encoder open and exhaust the GPU's encode-session limit under rapid reconnects.
-pub(crate) static CURRENT_MON_GEN: AtomicU64 = AtomicU64::new(0);
-
 /// IDD-push mode: a new client connection preempts + recreates the monitor (single-client reconnect),
 /// because a REUSED IddCx monitor's swap-chain is dead. Off → monitors are shared across sessions.
 fn idd_push_mode() -> bool {
@@ -590,7 +584,6 @@ fn mgr_acquire(mode: Mode) -> Result<VirtualOutput> {
         let pm = Some((mon.mode.width, mon.mode.height, mon.mode.refresh_hz));
         let target = mon.target();
         let gen = mon.gen;
-        CURRENT_MON_GEN.store(gen, Ordering::Relaxed);
         return Ok(VirtualOutput {
             node_id: 0,
             preferred_mode: pm,
@@ -617,7 +610,6 @@ fn mgr_acquire(mode: Mode) -> Result<VirtualOutput> {
     let pm = Some((mon.mode.width, mon.mode.height, mon.mode.refresh_hz));
     let target = mon.target();
     let gen = mon.gen;
-    CURRENT_MON_GEN.store(gen, Ordering::Relaxed);
     g.state = MgrState::Active { mon, refs: 1 };
     Ok(VirtualOutput {
         node_id: 0,