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-presenter/src/overlay.rs

@@ -37,6 +37,11 @@ pub struct FrameCtx<'a> {
     pub stats: Option<&'a str>,
     /// The capture hint (bottom-center pill, "click to capture…"); `None` = hidden.
     pub hint: Option<&'a str>,
+    /// A mid-stream Match-window resize is in flight (design/midstream-resolution-resize.md,
+    /// client UX): draw a full-screen scrim + spinner so the host's 0.3–2 s virtual-display
+    /// and encoder rebuild reads as an intentional pause rather than the stream stretching to
+    /// the changed window. Cleared the instant the sharp new-resolution frame is on glass.
+    pub resizing: bool,
     /// The active gamepad's name (the console library's controller chip).
     pub pad: Option<&'a str>,
     /// The active pad's resolved kind — drives the console UI's button glyphs