refactor(studio): simplify hooks, split contexts, remove dead code (#1416)

* fix(studio): guard Zustand no-op setters and fix useConsoleErrorCapture memory leak

- Guard setIsPlaying to skip set() when value unchanged (eliminates 60
  notifications/sec during reverse playback)
- Guard caption store selectGroup to bail before set() when group missing
  (prevents empty Zustand notifications)
- Guard clearSelection to skip when already empty
- Fix useConsoleErrorCapture: restore original console.error, remove error
  event listener, and delete __hfErrorCapture flag on cleanup

* fix(studio): delete dead files and unused exports

Remove 7 dead files (audioBeatDetection, keyframeSnapping,
timelineInspector, DopesheetStrip, StaggerControls,
TimelineLayerPanel, TimelineEditorNotice) and their test companions.

Delete unused computeFitToChildrenSize export from propertyPanelHelpers.

Fix re-export indirection: useDomEditCommits and studioMotionOps.test
now import patch builders directly from manualEditsDomPatches instead
of the re-export passthrough in manualEditsDom.

* fix(studio): eliminate effect-chain state mirroring for lint findings, hover, and GSAP fetch

Move lint findingsByElement sync from App.tsx into useLintModal where
the value is produced, removing the mirroring useEffect. Consolidate
4 hover-clearing effects in useDomSelection into 2 (one unconditional
on context change, one conditional combining caption mode, selection
match, and disconnected element checks). Fold the GSAP retry effect
into the fetch effect in useGsapTweenCache, scheduling a single retry
via setTimeout when the initial fetch returns 0 animations.

Eliminates 3 unnecessary render cycles from effect chains.

* fix(studio): memoize renderQueue, toolbar, and canvas rect to prevent re-render cascade

- Wrap renderQueue object in useMemo so StudioContext consumers don't
  re-render on every App render
- Memoize timelineToolbar JSX so NLELayout memo isn't defeated
- Move canvasRect getBoundingClientRect() from render-time IIFE to a
  useLayoutEffect-backed ref, eliminating layout thrashing
- Track and clear setTimeout handles in refreshPreviewDocumentVersion
  to prevent stale timer accumulation on rapid calls and unmount

* refactor(studio): consolidate GSAP shared primitives — defaults, iframe access, keyframe parsing

Extract duplicated PROPERTY_DEFAULTS, IframeGsap interface, iframe
accessors (getIframeGsap, queryIframeElement), percentage keyframe
parsing, and toAbsoluteTime into a single gsapShared.ts module.

Removes ~120 lines of copy-pasted logic across 8 hook files, reducing
drift risk between the duplicate implementations.

* fix(studio): remove dead store fields, dead file, duplicate helper, and unsafe assertions

* refactor(studio): deduplicate selector helpers, rounding utils, percentage computation, and iframe access

* fix(studio): split StudioContext into Shell + Playback to prevent cascade re-renders

* refactor(studio): decompose useGsapScriptCommits into focused mutation hooks

* refactor(studio): decompose useFileManager into focused file operation hooks

Extract useFileTree (tree loading, refresh, derived assets/compositions)
and useEditorSave (debounced save with history tracking) from the 508-LOC
useFileManager. The parent hook composes both and retains file I/O,
click-to-source, upload/import, and CRUD — preserving the same public
interface so no consumers change.

* refactor(studio): decompose useDomEditCommits into focused commit hooks

Extract geometry (path offset, box size, rotation) and element lifecycle
(delete, z-index reorder) into useDomGeometryCommits and
useElementLifecycleOps. Parent keeps persistDomEditOperations as core
and composes all sub-hooks — public interface unchanged.

* refactor(studio): simplify useAppHotkeys with declarative command table

* refactor(studio): simplify useAppHotkeys with declarative command table

Replace 15 individual useRef callback refs with a single cbRef object.
Extract keydown dispatch into pure dispatchModifierKey/dispatchPlainKey
functions. Merge duplicate undo/redo logic into shared applyHistory.
Extract cross-origin listener boilerplate into safeAddListener/safeRemoveListener.

Hook body: 204 LOC (down from 445). Public API unchanged.

* fix(studio): remove unused getDomEditTargetKey import

* refactor(studio): decompose useDomEditSession into focused editing hooks

Extract GSAP-aware geometry intercepts (move/resize/rotation) and
animated property commit into useGsapAwareEditing, and selection
wiring, GSAP cache management, preview sync, and selection handlers
into useDomEditWiring. The parent remains a pure composition shell.

* style(studio): fix formatting in 5 files

* fix(studio): trim App.tsx to 598 lines (under 600 limit)

---------

Co-authored-by: Miguel Ángel <miguel07alm@protonmail.com>

packages/studio/src/utils/timelineAssetDrop.ts

@@ -1,4 +1,6 @@
 import { AUDIO_EXT, IMAGE_EXT, VIDEO_EXT } from "./mediaTypes";
+import { roundToCenti } from "./rounding";
+import { COMPOSITION_ROOT_OPEN_TAG_RE } from "./studioHelpers";
 
 export const TIMELINE_ASSET_MIME = "application/x-hyperframes-asset";
 export const TIMELINE_BLOCK_MIME = "application/x-hyperframes-block";
@@ -51,13 +53,13 @@ export function buildTimelineFileDropPlacements(
   durations: number[],
   occupiedClips: Array<{ start: number; duration: number; track: number }> = [],
 ): Array<{ start: number; track: number }> {
-  let nextStart = Math.round(Math.max(0, placement.start) * 100) / 100;
+  let nextStart = roundToCenti(Math.max(0, placement.start));
   const sequenceStart = nextStart;
   const resolvedDurations = durations.map((duration) =>
     Number.isFinite(duration) && duration > 0 ? duration : FALLBACK_TIMELINE_FILE_DROP_DURATION,
   );
   const sequenceEnd = resolvedDurations.reduce(
-    (end, duration) => Math.round((end + duration) * 100) / 100,
+    (end, duration) => roundToCenti(end + duration),
     sequenceStart,
   );
   const overlapsDropTrack = occupiedClips.some((clip) => {
@@ -72,7 +74,7 @@ export function buildTimelineFileDropPlacements(
 
   return resolvedDurations.map((duration) => {
     const start = nextStart;
-    nextStart = Math.round((nextStart + duration) * 100) / 100;
+    nextStart = roundToCenti(nextStart + duration);
     return { start, track };
   });
 }
@@ -120,8 +122,7 @@ export function buildTimelineAssetInsertHtml(input: {
 }
 
 export function insertTimelineAssetIntoSource(source: string, assetHtml: string): string {
-  const rootOpenTag = /<[^>]*data-composition-id="[^"]+"[^>]*>/i;
-  const match = rootOpenTag.exec(source);
+  const match = COMPOSITION_ROOT_OPEN_TAG_RE.exec(source);
   if (!match || match.index == null) {
     throw new Error("No composition root found in target source");
   }