feat(sdk): file-backed fs adapter + setTiming GSAP-script sync; add sdk-playground

[vanceingalls]

Stacked on the acorn-parser/T6e branch.

What

• fs PersistAdapter implemented (was a stub) — packages/sdk/src/adapters/fs.ts. node:fs/promises read/write, timestamped version history under .hf-versions/<path>/, prune to maxVersions (20), listVersions/loadFrom. Emits persist:error in the canonical { error: { message, cause } } shape.
• setTiming GSAP-script sync — packages/sdk/src/engine/mutate.ts. setTiming on a GSAP composition stamped data-start/data-end on the DOM node, but the runtime re-stamps those attributes from GSAP positions on the next init — silently overwriting the edit. handleSetTiming now also rewrites the GSAP script (parseGsapScriptAcornForWrite + updateAnimationInScript), flushing both models in one patch pair so they stay in sync. DAW-style timeline trim depends on this.
• @hyperframes/sdk-playground (new, private) — interactive browser harness over the full op surface: setStyle/setText/setAttribute/removeElement/setVariableValue/find/selection() proxy/all 9 GSAP+label ops/setClassStyle. Live preview iframe with click-select + drag-to-reposition, DAW-style timeline trim via setTiming, file-backed persistence with version history (Vite dev-server plugin + fetch adapter), undo/redo/can/getOverrides/flush, raw-HTML editor modal. README documents built vs planned.

Test

• bun run --cwd packages/sdk build + test — 118 pass
• bun run --cwd packages/sdk-playground build — clean
• oxlint + oxfmt clean; fallow audit passes (0 introduced findings)

🤖 Generated with Claude Code

[vanceingalls]

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(sdk): stage 6 — sub-composition scoped ids (F9) #1434
• feat(sdk): stage 5 — export adapter factories from package root #1432
• docs(sdk-playground): accurate README with stage coverage and CanResult #1429
• feat(sdk): stage 4 — canUndo/canRedo, removeElement GSAP cascade, override-set cleanup #1431
• feat(sdk): can() returns CanResult; T4 dispatch-boundary tests #1426
• fix(sdk): fs adapter flush() tracks in-flight writes; add to T13 contract suite #1425
• feat(sdk): file-backed fs adapter + setTiming GSAP-script sync; add sdk-playground #1423 👈 (View in Graphite)
• refactor(core): swap studio-api read path from recast to acorn parser (T6e) #1392
• feat(core): parse-parity suite for acorn parser (T6d) #1370 : 1 other dependent PR (#1379 )
• feat(core): acorn GSAP write path — magic-string offset-splice (T6c) #1369
• feat(core): acorn GSAP read path with T6b differential corpus tests #1368
• main

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