feat(studio): asset click policy and canvas nudge gate

[ukimsanov]

What

two small pure modules with tests — assetClickBehavior (click vs double-click policy for sidebar assets) and canvasNudgeGate (debounce gate for arrow-key canvas nudges).

Why

policy dependencies of the upcoming asset card and nudge hook, reviewable as plain decision tables.

How

new files only.

Test plan

bunx vitest run on both test files; tsc --noEmit; fallow audit clean.

---

Stack position 9/25 — 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]

• 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
• 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 👈 (View in Graphite)
• 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

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[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]

Verdict: LGTM (green) — small, sharp, correctly bounded

Two pure helpers plus a module-level singleton claim gate. The scope is deliberately narrow; each unit is exercised at its edges. No unit-consistency traps (both files are pixel-only or dimensionless).

The pointed queries

• Click-vs-drag threshold (fair tie-break). packages/studio/src/utils/assetClickBehavior.ts:73–:75 — isPointerClick(dx, dy) = Math.abs(dx) < 4 && Math.abs(dy) < 4. Strict < at the boundary; exactly 4px is a drag, not a click. Deterministic and symmetric across axes. Test at :94–:98 pins the boundary in both directions (positive AND negative displacement); :100–:103 confirms the sign symmetry.
• findClipForAsset — matcher normalisation. :43–:61 handles the four src shapes documented by deriveUsedPaths (absolute URL, /api/projects/.../preview/..., ./-prefixed, bare relative), plus query-string stripping and percent-decode. Every shape has a dedicated test at :26–:60. The earliest start deterministic pick at :62–:67 avoids returning an arbitrary duplicate. Robust.
• Nudge gate — nesting semantics. packages/studio/src/utils/canvasNudgeGate.ts:10–:26 — module-level claims: number counter; acquireCanvasNudgeKeys() returns an idempotent release closure that decrements at most once. Test at :16–:24 verifies double-release is a no-op (guarded by the released flag at :16). Correct for nested overlays.
• Wiring with #2203 (canvas nudge math). No direct import at these PR SHAs — canvasNudgeGate.ts doesn't reference domEditNudge.ts and vice versa. That's expected: this PR ships the gate, #2203 ships the delta math, and a downstream PR (per .fallowrc.jsonc markers, studio-dnd/pr22) wires both into DomEditOverlay. As long as the eventual consumer acquires the gate BEFORE binding its arrow-key listener and releases it on unmount, the ownership arbitration between DomEditOverlay and usePlaybackKeyboard (documented at :5–:8) will hold. No coupling to inspect here.

Nits (non-blocking)

• The module-level claims counter in canvasNudgeGate.ts persists across tests within a Vitest worker. Currently both tests clean up to zero, but there is no beforeEach(() => { /* reset */ }) — if a future test throws mid-way and leaks a claim, the next test's initial expect(claimed()).toBe(false) would fail without an obvious signal. A beforeEach guard, or exposing a __resetForTests() helper, would future-proof this. Cosmetic — the current tests happen to be well-behaved.

R1 by Via

[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.