feat(studio): NLE shell components — context provider, panes, overlays (unwired)

[ukimsanov]

What

the NLE shell layer, unwired: NLEContext (provider extracted from NLELayout), PreviewPane, AssetPreviewOverlay + assetPreviewStore, TimelineOverlays (menus/modal/hint extracted from Timeline), timelineClipChildren, timelineClipDragTypes, useTimelinePlayerLoop (playback loop extracted from useTimelinePlayer).

Why

the extracted replacements for NLELayout/StudioPreviewArea and the oversized Timeline/useTimelinePlayer internals, reviewable standalone.

How

new files only, tsc-clean against main. They intentionally duplicate blocks of their still-alive originals (duplication is warn-level in fallow; the swap PRs delete the originals). Dead-file findings covered by TEMP(studio-dnd) entry registrations, removed at the app-shell swap.

Test plan

tsc --noEmit; bunx vitest run (suite unchanged); fallow audit clean.

---

Stack position 13/25 — studio NLE overhaul (CapCut-parity timeline + canvas). Graphite manages bases; merge from #2192 upward. Temporary TEMP(studio-dnd) fallow entries (unwired-component windows) are all removed by #2213 (app-shell swap), whose tree is byte-identical to the fully-verified integration branch.

[ukimsanov]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• feat(studio): assets/blocks panel behaviors + preview helpers #2216
• feat(studio): timeline visual refresh #2215
• feat(studio): clip thumbnail modules #2214
• feat(studio): app shell swap — mount EditorShell, retire the legacy engine #2213
• feat(studio): timeline glue swap — Timeline/TimelineCanvas onto the NLE engine #2212
• feat(studio): canvas glue swap — overlay, gestures, selection to final form #2211
• feat(studio): sidebar asset card (unwired) #2210
• feat(studio): NLE shell assembly (unwired) #2209
• feat(studio): canvas chrome components (unwired) #2208
• feat(studio): timeline interaction hooks and lanes component (unwired) #2207
• feat(studio): clip drag engine — preview and commit (unwired) #2206
• feat(studio): glue API coexistence layer for the NLE swap #2205
• feat(studio): NLE shell components — context provider, panes, overlays (unwired) #2204 👈 (View in Graphite)
• feat(studio): arrow-key nudge step math (unwired) #2203
• feat(studio): canvas context menu and z-order actions (unwired) #2202
• test(studio): characterization suites for resize commit and razor history #2201
• feat(studio): asset click policy and canvas nudge gate #2200
• feat(studio): timeline lane-zone model #2199
• feat(studio): timeline z-stacking sync model #2198
• feat(studio): multi-clip drag preview math #2197
• feat(studio): timeline magnetic snapping #2196
• feat(studio): timeline collision and placement model #2195
• feat(studio-server): files route extensions #2194
• feat(studio): seek-restore contract for player reloads #2193
• feat(studio): timeline leaf helpers — audio inspector, zoom math, UI prefs #2192
• main

This stack of pull requests is managed by Graphite. Learn more about stacking.

[miga-heygen]

Reviewed as part of the 25-PR NLE overhaul stack. Full stack review on #2205 (the keystone). No blockers on this PR. — Miga

[vanceingalls]

R1 — Batch C (unwired chrome / assembly)

Verdict: 🟢 approve

Reviewed at ba130cb9. Focus per Phase-2 recon: NLEContext extraction from NLELayout must be behavior-preserving; new components must be truly unwired at merge; fallow entries must be tracked for #2213 removal.

Extraction correctness — 🟢

NLEContext.tsx is a duplicate-then-swap extraction, not an in-place refactor. NLELayout.tsx is untouched at this SHA (confirmed via file-changed set: 10 files, none of them NLELayout.tsx). StudioPreviewArea.tsx:382 continues to mount NLELayout; the pre-swap render path is unchanged. Extraction cannot regress pre-swap consumers because their code path is untouched.

The extracted NLEProvider faithfully copies the provider-shape state from NLELayout: player hook, useCompositionStack, timelineH persistence + restore clamp, composition-loading gate, compIdToSrc fetch/patch, iframe onLoad + MotionPathPlugin preload, previewCompositionSize. The bits NLELayout owns and this provider omits (fullscreen useSyncExternalStore, usePreviewBlockDrop stage-ref, expanded-clip local-coordinate wrappers, Escape-to-pop keyboard, timelineVisible toggle) are picked up downstream — verified expandedParentStart + trackStudioExpandedClipEdit live in #2209's TimelinePane.tsx, and containerRef + Escape handler live in #2209's EditorShellBody.

Unwired assertion — 🟢

Grepped packages/studio/src/**/*.{ts,tsx} at this SHA for consumers of every new symbol; all imports resolve inside the new subtree only:

• NLEContext / NLEProvider / useNLEContext — consumed only by new PreviewPane.tsx (sibling); no live-tree consumer.
• AssetPreviewOverlay — consumed only by new PreviewPane.tsx.
• PreviewPane — no live-tree consumer.
• TimelineOverlays — no consumer at all at this SHA (wired later).
• renderClipChildren (from new timelineClipChildren.tsx) — TimelineCanvas.tsx:197 defines a locally-scoped renderClipChildren arrow; the new module-scoped export is not imported by TimelineCanvas. Name shadow, no live consumption.
• timelineClipDragTypes — no consumer.
• useTimelinePlayerLoop — no consumer.
• assetPreviewStore — consumed only by new AssetPreviewOverlay.

Fallow lifecycle — 🟢

Added to .fallowrc.jsonc:

• unusedExports block: NLEContext.tsx, PreviewPane.tsx, AssetPreviewOverlay.tsx, TimelineOverlays.tsx, timelineClipChildren.tsx, timelineClipDragTypes.ts, useTimelinePlayerLoop.ts, assetPreviewStore.ts — 8 entries, all with the shared TEMP(studio-dnd) comment pointing at studio-dnd/pr22 for removal.
• complexity ignore block: TimelineOverlays.tsx (1 entry, same TEMP comment).

All 9 entries are on files created in this PR and are removable in one motion at #2213.

Notes for Phase 3 cross-check

🟡 NLEProvider sets DEFAULT_TIMELINE_H = 340 (line 22), while NLELayout uses DEFAULT_TIMELINE_H = 220 (line 80). Both are gated by the persisted readStudioUiPreferences().timelineHeight, so returning users see identical behavior. First-load-after-cutover for users without a persisted preference will jump from 220 to 340. Not a blocker on this unwired PR; flagging for Phase-3 so the #2213 review can confirm this is intentional (CapCut-style default per the comment) vs. an accidental drift.

R1 by Via

[ukimsanov]

Confirming the 340 vs 220 question: intentional. 340 is the CapCut-style taller timeline default the NLE shell was designed and feel-tested with; 220 was the legacy layout's value. First-load-after-cutover users without a persisted preference get the new default deliberately.

[miguel-heygen]

Current required CI is not clean: preview-regression is failing at head 37f90ba. Please rerun/fix and re-request review once green.

[miguel-heygen]

Re-reviewed current head and verified the addressed feedback and required behavior. Approval is for this exact head; Graphite mergeability may still be pending.

Superseded by current-head re-review; findings verified addressed.