change-spf-behavior

# Change an SPF behavior Treat code and tests as implementation truth. Read the behavior, composition site, state/context slots, helpers, and tests, then load only the relevant file from `internal/design/spf/conventions/`. Before acting, read the one detailed workflow that matches the requested change: - Purpose expands or changes: `references/update.md` - Purpose stays fixed while implementation improves: `references/refactor.md` - One responsibility splits by type or concern: `references/split.md` - Two responsibilities may become one: `references/merge.md` 1. State the current purpose, intended delta, and observable business rules. 2. Map inputs, writes, lifecycle gates, cleanup, ordering, and source-reset rules. 3. Choose the smallest destination shape that preserves those constraints. 4. Pin observable behavior with tests before changing implementation. 5. Re-read the final behavior without the diff and verify ownership, cleanup, composition, naming, and coverage. For a split, name the ownership axis and cross-boundary invariants. For a merge, confirm the result owns one coherent purpose; extract a helper when only an algorithm is shared. Ask for direction when alternatives materially change ownership or public contracts. Run the narrow affected tests, then as applicable: ```bash pnpm -F @videojs/spf test pnpm -F @videojs/spf build pnpm -F @videojs/spf size ``` ## Example Input: “Split source cleanup out of the playback lifecycle behavior.” Output: A documented ownership boundary, pinned invariants, focused implementation changes, and proportional SPF checks.