notion-react: v0.2 block-coverage follow-ups

Tracking epic for v0.2 block-coverage follow-ups identified in context/notion-block-coverage/gaps.md.

Must-haves for v0.1 live in separate issues (#585, #586, #587).

v0.2 checklist

• synced_block first-class component (synced_from original vs reference, children)
• callout icon: accept external / custom_emoji envelopes in addition to emoji string
• column.width_ratio prop
• code.caption prop
• bookmark.caption + embed.caption props
• table_of_contents.color + list-item color plumbing
• link_to_page: database_id + comment_id targets
• breadcrumb first-class component (replace Raw passthrough)
• child_database first-class component (read-only renderer, no creation path)
• heading_4 E2E coverage
• Media E2E coverage: Video, Audio, File, Pdf
• Table E2E coverage (blocked on #586)

Permanent skips

• tab, meeting_notes — no documented append path; keep BlockType literal, route through Raw.
• template — creation deprecated 2023-03-27; read-only Raw.
• link_preview — not API-creatable; read-only Raw.
• unsupported — opaque; read-only Raw.

Start with context/notion-block-coverage/gaps.md and review the separate v0.1 issues (#585, #586, #587) before selecting one v0.2 checklist item. Identify the relevant notion-react component or E2E entry point for that item; done means the selected behavior or coverage is implemented, while the documented permanent skips remain routed through Raw.