fix(capture/vdisplay): descriptor-following defers while a topology reassert is in flight

The exclusive-topology reassert's forced re-commit transiently bounces the
virtual display's mode; the descriptor poller can sample that EVICTION state
and recreate the ring at a mode the recovery chain is about to undo (field
log 2026-07-27 10:30:44Z: hdr=true → false → recreate → recovery restores
true → second recreate). New pf-win-display::topology_churn latch (deadline
semantics — self-expiring, so a lost release can never wedge descriptor-
following off): the watchdog holds it for interval+3s each fighting round and
releases on "stable again"; poll_display_hdr consumes samples but acts on
nothing while held — which also keeps the negotiated-depth pin-back from
issuing a CCD write mid-eviction, where it would fight the reassert itself.
The deliberate recreate_ring_in_place recovery path is unaffected.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

crates/pf-vdisplay/src/vdisplay/windows/manager.rs

@@ -865,11 +865,21 @@ impl VirtualDisplayManager {
                                 reasserts = fighting,
                                 "exclusive topology stable again — no non-managed display active"
                             );
+                            // Close the churn window early — descriptor-following resumes now
+                            // instead of waiting out the hold's self-expiry.
+                            pf_win_display::topology_churn::release();
                         }
                         fighting = 0;
                         continue;
                     }
                     fighting += 1;
+                    // Announce the churn BEFORE evicting: every descriptor the capturer's poller
+                    // samples from here until "stable again" (or self-expiry) is potentially the
+                    // TRANSIENT eviction state — acting on it would recreate the ring at a mode
+                    // the recovery chain is about to undo (the field hdr=true→false→true double
+                    // recreate). Window = watchdog interval + recovery/debounce margin, refreshed
+                    // every fighting round.
+                    pf_win_display::topology_churn::hold(interval + Duration::from_secs(3));
                     match fighting {
                         1..=3 => tracing::warn!(
                             survivors,