[codex] Normalize legacy tweet URL entities

[steipete]

What changed

• Fill missing expandedUrl and displayUrl values on legacy stored URL entities at the shared rendering boundary.
• Add regression coverage for old url/start/end-only rows.
• Document the compatibility fix in the changelog.

Why

Post-deploy production E2E found the all-time Bookmarks API returning 500 when a quoted tweet contained legacy URL metadata without expanded-link fields. The current API contract requires both fields, but old databases legitimately predate them.

Impact

Saved and quoted tweets now remain readable without rewriting the local database. Production-data proof changed Bookmarks from HTTP 500 to HTTP 200 in 333 ms.

Validation

• pnpm exec vitest run src/lib/tweet-render.test.ts src/lib/queries.test.ts --reporter=verbose — 59 tests
• pnpm check
• pnpm build
• Structured autoreview: clean, no actionable findings
• Production-data server smoke: Likes 200/1.21s, Bookmarks 200/333ms

[clawsweeper]

ClawSweeper status: review started.

I am starting a fresh review of this pull request: [codex] Normalize legacy tweet URL entities This is item 1/1 in the current shard. Shard 0/1.

This placeholder means the worker is alive and reading the current context. I will edit this same comment with the actual review when the claws are done clicking.

Crustacean status: shell secured, claws on keyboard, evidence pebbles being sorted.