fix(skills): align core contract with check

[miguel-heygen]

Summary

• add required root data-start="0" to the minimal composition skeleton and required-elements list
• make hyperframes check the single canonical quality gate in hyperframes-core
• replace the stale lint/validate/inspect gate in the shared brief contract
• pin both contracts with a skill-content regression test and refresh the skills manifest

Verification

• reproduced both mismatches on current main
• bun test packages/cli/src/commands/coreSkillContent.test.ts (2 passed)
• bun run lint:skills (20 skills, no issues)
• CLI typecheck passed
• oxlint/oxfmt and all pre-commit hooks passed

Out of scope signals from the same feedback

• Windows ASR auto-install and one-line remote font fetching are feature requests, not regressions
• Studio data-hf-id persistence is intentional under the existing editor persistence contract

[xiayewang-heygen]

LGTM — small, well-scoped doc/contract alignment. Verified both claims:

1. data-start="0" on the root IS enforced. packages/lint/src/rules/composition.ts:489-494 catches root elements missing data-start and errors with the exact same wording ("The runtime needs data-start=\"0\" on the root element to begin playback"). The minimal-composition skeleton was drifting from the lint contract; PR closes that gap.

2. check really is the canonical gate. packages/cli/src/commands/check.ts describes itself as "Run lint, runtime, layout, motion, and WCAG contrast verification in one browser session" — matches the new SKILL.md wording verbatim ("0 findings across lint, runtime, layout, motion, and contrast"). Consolidating three checklist items (two of which were duplicated check entries) into one is the right cleanup.

The regression test in coreSkillContent.test.ts pins both facts to the skill docs — that's the right shape for a contract-drift fix; if either contract wanders again, the test bites.

Review by WXai