Merge origin/main into the pf-capture sweep

Upstream landed `fc335b39` (negotiate the cursor around what the encoder can blend) on the same
files this sweep restructured. Merged rather than rebased: the sweep MOVED ~2,000 lines out of
`linux/mod.rs` into `pipewire.rs`/`portal.rs`/`pw_*.rs`, so a rebase would have re-fought the same
conflict in up to nine commits; merging resolves it once with both sides in view. The repo already
carries merge commits (`land/sweep-all`).

Two conflicts, both resolved by keeping BOTH changes:

* `linux/mod.rs` — `PortalCapturer::open` gains upstream's `want_metadata_cursor` AND keeps the
  sweep's `PortalSession` teardown, so the portal threads now take `(setup_tx, quit_rx,
  want_metadata_cursor)`. The second conflict was upstream editing inside the region Phase 5.1/5.3
  moved out; the split wins and upstream's change is ported to where the code now lives:
  `choose_cursor_mode`'s new `want_metadata` ladder (4 arms — prefer Embedded when the encoder can't
  blend, and warn-then-take Metadata when Embedded isn't advertised) is now in `portal.rs`, taken
  verbatim.
* `gamestream/stream.rs` — the pooled-capturer slot keeps upstream's third reuse key
  (`metadata_cursor`, beside HDR-ness) AND the sweep's `result.is_ok() && capturer.is_alive()`
  re-pool gate. Both guard the same slot against different failures: theirs against reusing a
  session negotiated for the wrong cursor mode, the sweep's (L2) against reusing a dead one.

Everything else auto-merged, including the `want_metadata_cursor` thread through
`host/capture.rs`'s facade and `native/stream.rs`'s `session_plan::cursor_blend_for`.

Verified after the merge: workspace `cargo test` green, `clippy --workspace --all-targets` clean on
Linux AND on x86_64-pc-windows-msvc, `cargo fmt --check --all` clean, pf-capture 38/38.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

crates/punktfunk-host/src/capture.rs

@@ -66,8 +66,14 @@ fn zero_copy_policy(
 /// Open a live capturer for a client-sized monitor via the xdg ScreenCast portal. `want_hdr`
 /// offers the GNOME 50+ 10-bit PQ/BT.2020 formats (pass it only when the session negotiated HDR
 /// AND the mirrored monitor is in HDR mode — see [`pf_capture::gnome_hdr_monitor_active`]).
+/// `want_metadata_cursor` asks for cursor-as-metadata — pass it only when the session's encode
+/// backend composites `CapturedFrame::cursor` (`encode::cursor_blend_capable`); otherwise the
+/// portal embeds the pointer, so no backend × cursor-mode combination streams cursorless.
 #[cfg(target_os = "linux")]
-pub fn open_portal_monitor(want_hdr: bool) -> Result<Box<dyn Capturer>> {
+pub fn open_portal_monitor(
+    want_hdr: bool,
+    want_metadata_cursor: bool,
+) -> Result<Box<dyn Capturer>> {
     // On RemoteDesktop-capable desktops (KWin/GNOME) anchor ScreenCast to a RemoteDesktop
     // session so it inherits that grant headlessly; wlroots/Sway has no RemoteDesktop portal,
     // so use a plain ScreenCast session there.
@@ -76,11 +82,19 @@ pub fn open_portal_monitor(want_hdr: bool) -> Result<Box<dyn Capturer>> {
     // passthrough is virtual-output-only; the global encoder-pref lever still applies inside.
     // Native NV12 stays off too: the mirror path doesn't resolve the codec here, and the desktop
     // compositors it mirrors (GNOME/KWin) don't produce NV12 anyway.
-    pf_capture::open_portal_monitor(anchored, want_hdr, zero_copy_policy(false, false))
+    pf_capture::open_portal_monitor(
+        anchored,
+        want_hdr,
+        want_metadata_cursor,
+        zero_copy_policy(false, false),
+    )
 }
 
 #[cfg(not(target_os = "linux"))]
-pub fn open_portal_monitor(_want_hdr: bool) -> Result<Box<dyn Capturer>> {
+pub fn open_portal_monitor(
+    _want_hdr: bool,
+    _want_metadata_cursor: bool,
+) -> Result<Box<dyn Capturer>> {
     anyhow::bail!("portal capture requires Linux (xdg-desktop-portal + PipeWire)")
 }