feat(studio): keyframe system — parser, runtime, timeline UI, design panel, gesture recording (#1311)

* feat(studio): runtime hooks — global time compiler + keyframe runtime

Add the runtime bridge layer: global time compilation (tween % → clip %),
soft reload after mutations, runtime keyframe preview, and keyframe
commit helper.

* feat(studio): runtime hooks — global time compiler + keyframe runtime

Add the runtime bridge layer: global time compilation (tween % → clip %),
soft reload after mutations, runtime keyframe preview, and keyframe
commit helper.

* feat(studio): keyframe cache + commit hooks

Add hooks for keyframe cache population (tween → clip-relative %),
mutation dispatch, keyframe snapping, and audio beat detection.

* feat(studio): timeline UI — dopesheet diamonds + keyboard nav

Add dopesheet strip with diamond keyframe indicators, timeline property
rows, keyboard navigation (J/Shift+J/Delete/K), and feature gate
(STUDIO_KEYFRAMES_ENABLED defaults to false).

* feat(studio): design panel — arc controls + ease curve + stagger

Add arc path controls (curviness slider, auto-rotate), motion path SVG
overlay, ease curve visualization, stagger controls, and expanded
animation card. Includes border-radius editor dependency from #1217.

* feat(studio): gesture recording core

Add gesture recording engine with RAF sampling, modifier key property
mapping (Shift→rotationXY, Alt→rotation, Cmd→opacity),
Ramer-Douglas-Peucker simplification, and ghost trail SVG overlay.

* fix(studio): keyframe drag + recording bug bash

21 fixes: capture GSAP base at drag start, translate:none before
gsap.set, skip reapplyPathOffsets for GSAP elements, clamp recording
seek, _auto flag for 100% keyframes, overlay flash fix, block edits
during recording.

* feat(studio): keyframe integration wiring + docs

Wire App.tsx recording orchestration, TimelineToolbar K/R buttons,
PropertyPanel per-property diamonds, shortcuts panel, toast
notifications, and keyframes guide documentation. All gated on
STUDIO_KEYFRAMES_ENABLED (default false).

packages/studio/src/player/components/ShortcutsPanel.tsx

@@ -17,6 +17,46 @@ const SHORTCUT_SECTIONS = [
       { key: "F", label: "Toggle fullscreen" },
     ],
   },
+  {
+    title: "Keyframes",
+    hints: [
+      { key: "K", label: "Add keyframe at playhead" },
+      { key: "Del", label: "Delete selected keyframe" },
+      { key: "H", label: "Toggle hold / bezier" },
+      { key: "U", label: "Expand / collapse properties" },
+      { key: "R", label: "Record gesture" },
+    ],
+  },
+  {
+    title: "Editing",
+    hints: [
+      { key: "⌘Z", label: "Undo" },
+      { key: "⌘⇧Z", label: "Redo" },
+      { key: "⌘C", label: "Copy element" },
+      { key: "⌘V", label: "Paste element" },
+      { key: "⌘X", label: "Cut element" },
+      { key: "S", label: "Split clip at playhead" },
+      { key: "Del", label: "Delete selected element" },
+    ],
+  },
+  {
+    title: "Gesture recording modifiers",
+    hints: [
+      { key: "Drag", label: "Record x / y position" },
+      { key: "Scroll", label: "Record z depth" },
+      { key: "⇧ Drag", label: "Record rotationX / rotationY" },
+      { key: "⌥ Drag", label: "Record rotation" },
+      { key: "⌘ Drag↕", label: "Record opacity" },
+      { key: "⌘ Scroll", label: "Record scale" },
+    ],
+  },
+  {
+    title: "Panels",
+    hints: [
+      { key: "⌘1", label: "Compositions tab" },
+      { key: "⌘2", label: "Assets tab" },
+    ],
+  },
   {
     title: "Work area",
     hints: [