refactor(host/W6.2): extract the Windows display-topology cluster into the pf-win-display leaf crate

windows/{win_display,monitor_devnode,display_events}.rs move into
crates/pf-win-display: the CCD/GDI path-activation + mode-set + HDR
advanced-colour + source-rect helpers, the PnP monitor-devnode enable/disable
lever, and the WM_DISPLAYCHANGE / device-arrival watch. The coming pf-capture
crate's IDD-push capturer consumes all three; the host's pf-vdisplay backend
consumes win_display + monitor_devnode. A leaf lets both depend on them as a
PEER instead of the capturer reaching back into the orchestrator (plan §W6).

win_display's one external tie (crate::vdisplay::Mode) becomes the underlying
punktfunk_core::Mode; the cluster is otherwise self-contained (pf-paths for the
state file, serde_json for it, windows). pub(crate) items bump to pub at the
boundary; win_display carries a module-level allow(missing_safety_doc) to keep
the pre-carve behavior (the FFI helpers were pub(crate) unsafe fn with prose
safety docs — the lint only fires once they're pub, and this is an internal
publish=false leaf). The host imports the three modules at its crate root, so
every crate::{win_display,monitor_devnode,display_events}::* path is unchanged.

Verified: Linux clippy -D warnings (leaf empty + host
nvenc,vulkan-encode,pyrowave --all-targets); Windows clippy -D warnings
(pf-win-display --all-targets + host nvenc,amf-qsv --all-targets) Finished exit 0.

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

crates/punktfunk-host/Cargo.toml

@@ -22,6 +22,9 @@ pf-zerocopy = { path = "../pf-zerocopy" }
 # Shared frame/format vocabulary (CapturedFrame/PixelFormat/…), HDR metadata, thread QoS, and the
 # Windows DXGI capture identity — the leaf both capture and encode speak (plan §W6).
 pf-frame = { path = "../pf-frame" }
+# Windows display-topology helpers (CCD/GDI mode-set, PnP monitor devnodes, display-change watch),
+# extracted to a leaf crate (plan §W6). Empty on non-Windows, so it lives in the main deps.
+pf-win-display = { path = "../pf-win-display" }
 # M3 native control plane (the `punktfunk/1` QUIC handshake; data plane stays native-thread UDP).
 quinn = "0.11"
 anyhow = "1"