fix(clients): GTK + Decky polish batch from live Deck/Windows testing

GTK Linux client:
- hosts/library: clicking a card was dead — the handler was on
  FlowBoxChild::activate (never emitted on click); bridge child-activated
  → child.activate() on the FlowBox (ui_hosts, ui_library).
- stream: the Ctrl+Alt+Shift+D/Q/S chords (and all key forwarding) were
  dropped because the key controller sat on the overlay, which loses focus
  to the header back button after nav.push+fullscreen — move it to the
  window and remove it on teardown.
- video: a mid-session VAAPI decode error rebuilt a software decoder but
  never requested a keyframe, so under the infinite GOP the picture stayed
  gray/frozen forever. Request an IDR on any VAAPI error, keep the hardware
  decoder, and demote to software only after repeated failures.
- stream: fix a per-session Capture↔overlay reference cycle that leaked the
  overlay subtree + the Arc<NativeClient> on every session end — hold the
  overlay weakly.
- stream: accumulate the fractional wheel remainder so precision-scroll
  (Deck trackpad / hi-res wheels) sub-unit deltas aren't dropped.
- gamepad library: keep the launcher smooth on the Deck — freeze the aurora
  and trim the visible card range (fewer 3D offscreen passes) on low-power.
- gamepad: log full pad identity (vid:pid:name:type:virtual) on attach to
  diagnose an empty controller list on the Deck.
- cli: --connect host:<badport> silently did nothing; default to 9777 + warn.
- css: add the missing .pf-neutral pill rule; fix the clipped most-recent
  accent (inset outline instead of a corner-clipped box-shadow bar).

Decky plugin:
- surface the on-screen library browser: label the host-row Games button.
- fix silent pin data-loss — the detached Games modal captured a frozen
  pins array, so pinning a second game clobbered the first; mirror pins in
  a ref and track the modal's pinned ids locally for a live label.
- route pair-required hosts through the pairing modal from the fullscreen
  Stream button (parity with the QAM panel).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

clients/linux/src/app.rs

@@ -22,10 +22,14 @@ const CSS: &str = "
            color: alpha(currentColor, 0.8); background: alpha(currentColor, 0.1); }
 .pf-pill.pf-green { color: @success_color; background: alpha(@success_color, 0.15); }
 .pf-pill.pf-accent { color: @accent_color; background: alpha(@accent_color, 0.15); }
+.pf-pill.pf-neutral { color: alpha(currentColor, 0.75); background: alpha(currentColor, 0.12); }
 .pf-pip { min-width: 8px; min-height: 8px; border-radius: 999px;
           background: alpha(currentColor, 0.35); }
 .pf-pip.pf-online { background: @success_color; }
-.pf-recent { box-shadow: inset 3px 0 0 0 @accent_bg_color; }
+/* Most-recent host: a full accent ring drawn as an inset outline so it follows the card's
+   rounded corners (an `inset` box-shadow bar gets eaten by the 12px corner clip) and leaves
+   the card's own elevation shadow intact. */
+.pf-recent { outline: 2px solid @accent_color; outline-offset: -2px; }
 .pf-discovered { border: 1px dashed alpha(currentColor, 0.35); }
 .pf-poster { border-radius: 10px; background: alpha(currentColor, 0.08); }
 .pf-poster-monogram { font-size: 2.4em; font-weight: bold; color: alpha(currentColor, 0.45); }