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/pf-capture/src/lib.rs

@@ -515,15 +515,25 @@ pub mod synthetic_nv12;
 /// `want_hdr` offers the GNOME 50+ HDR formats (10-bit PQ/BT.2020 dmabufs) instead of the SDR
 /// set — pass it only when the mirrored monitor is actually in HDR mode (the host probes
 /// DisplayConfig) or the negotiation runs into its 10 s timeout and latches the SDR downgrade.
-/// The [`ZeroCopyPolicy`] carries the pre-resolved encode-backend facts (the one-way edge).
+/// `want_metadata_cursor` asks for cursor-as-metadata (`SPA_META_Cursor`) — pass it only when
+/// the session's encode path composites `CapturedFrame::cursor` (the host consults
+/// `pf-encode`'s `cursor_blend_capable`); otherwise the portal EMBEDS the pointer so it is
+/// never silently lost. The [`ZeroCopyPolicy`] carries the pre-resolved encode-backend facts
+/// (the one-way edge).
 #[cfg(target_os = "linux")]
 pub fn open_portal_monitor(
     anchored: bool,
     want_hdr: bool,
+    want_metadata_cursor: bool,
     policy: ZeroCopyPolicy,
 ) -> Result<Box<dyn Capturer>> {
-    linux::PortalCapturer::open(anchored, want_hdr && !hdr_capture_failed(), policy)
-        .map(|c| Box::new(c) as Box<dyn Capturer>)
+    linux::PortalCapturer::open(
+        anchored,
+        want_hdr && !hdr_capture_failed(),
+        want_metadata_cursor,
+        policy,
+    )
+    .map(|c| Box::new(c) as Box<dyn Capturer>)
 }
 
 /// Open the Linux portal capturer bound to an already-created virtual output's PipeWire node. The