feat(resize): scrim+spinner resize overlay in the shared presenter (Windows + GTK4)

The mid-stream Match-window trigger + Resolution tri-state already shipped on BOTH
desktop clients via the session-always punktfunk-session binary (pf-presenter D1/D2,
C1). This ports the last Apple-parity piece — the resize-in-progress indicator
(clients/apple ResizeIndicator/ResizeIndicatorView) — into the SHARED pf-presenter
overlay, so one implementation covers both the Windows and GTK4 session windows.

- ResizeIndicator (run.rs): the Apple state machine in Rust — `steering` (a switch was
  requested) shows it, `decoded` (a frame reached the target size) clears it, `tick`
  times it out after 2.5 s for a switch the host rejected/capped. The live drag stays
  sharp; only the host's 0.3-2 s virtual-display + encoder rebuild gap is covered. A
  present-while-resizing path keeps the spinner animating through that frame-less gap.
- DecodedImage::dimensions() (pf-client-core): the END signal — a decoded frame at the
  target size means the sharp new-mode picture is on glass (the accept ack alone lands
  ahead of the host's rebuild). Mirrors is_keyframe()'s cfg arms.
- FrameCtx.resizing (pf-presenter/overlay.rs) + Skia draw (pf-console-ui): a full-screen
  55% scrim + the shared rotating theme::spinner + "Resizing…" label. The overlay
  composites its own RGBA quad and can't sample the video to blur it as SwiftUI does, so
  a scrim stands in for the blur — same intent, one draw. resizing_since clocks the
  spinner; Drawn.resize_step defeats the damage gate so it redraws each frame.

Verified on Linux: pf-presenter/pf-console-ui/session/linux-client build + clippy
-D warnings clean; 8 pf-presenter tests green incl. 2 new ResizeIndicator tests.
Windows session-binary compile (cfg-symmetric) + live on-glass both pending.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

crates/pf-client-core/src/video.rs

@@ -183,6 +183,20 @@ impl DecodedImage {
             DecodedImage::D3d11(f) => f.keyframe,
         }
     }
+
+    /// The decoded image's pixel dimensions. The presenter's resize indicator uses these
+    /// as the mid-stream-resize END signal: a frame arriving at the target size means the
+    /// new-mode picture is on glass (the ack alone lands before the host's rebuild does).
+    pub fn dimensions(&self) -> (u32, u32) {
+        match self {
+            DecodedImage::Cpu(f) => (f.width, f.height),
+            #[cfg(target_os = "linux")]
+            DecodedImage::Dmabuf(f) => (f.width, f.height),
+            DecodedImage::VkFrame(f) => (f.width, f.height),
+            #[cfg(windows)]
+            DecodedImage::D3d11(f) => (f.width, f.height),
+        }
+    }
 }
 
 /// The Y′CbCr→RGB conversion as three vec4 rows for a shader constant buffer / push-constant