fix(lint): reject timeline content beyond render duration

[L1337H]

Summary

• fail lint when a visible timed element ends more than one frame beyond an explicit composition duration
• keep inferred-duration compositions, hidden timeline material, media source trims, and unresolved relative starts untouched
• report the exact element end, render boundary, and both valid fixes

Why

An explicit root data-duration is the hard export boundary. Previously, a child could extend far beyond it while hyperframes check still passed, so previews or snapshots could make unreachable timeline content look valid before export truncated it.

Verification

• bun run --cwd packages/lint test — 542 passed
• bun run build
• bun run lint
• bun run --cwd packages/lint typecheck
• scanned 1,023 repository HTML compositions — no new findings after frame-aware tolerance
• CLI repro: 10s root + 48.47s timed child fails hyperframes check --json with timed_element_exceeds_composition; shortening the child to 10s passes the full check

[L1337H]

@miguel-heygen could you please approve the fork workflows and review this focused lint fix? Local lint, build, 542 lint-package tests, a 1,023-composition compatibility scan, and the CLI fail/pass repro are all green.

[L1337H]

@miguel-heygen all required checks are green and the PR is approved. GitHub will not allow me to merge or enable auto-merge because the base-branch policy requires maintainer permissions. Could you merge it when convenient? Once merged, I will continue with the release and Fiona Dev rollout.