Add read-only Research workspace

[CountableNewt]

Summary

• add a read-only Research destination for the linked account
• aggregate the account's own Semble collections and cards plus current Margin annotations
• keep each research source independently available with safe links and responsive navigation

Implementation notes

• the authenticated /api/research route derives the linked DID from the browser session; clients cannot select another account
• research uses public PDS record reads, so no new OAuth scope is required
• pagination is cycle-safe, ownership is validated, Semble removals are applied, and records are sorted newest-first
• source failures are isolated so a Semble outage does not hide Margin data and vice versa
• the UI is browse-only: it does not create drafts or write to either source

Testing

• bun run verify
• 19 editor tests
• 91 web tests
• 77 Swift tests
• frontend typecheck, lint, and production build
• Swift release build
• browser QA at 1280×720 and 320×720, including Semble-to-Margin interaction, no console errors, and no horizontal overflow

Risk and rollout

• live source availability and upstream PDS record-shape drift remain external dependencies; partial failures are contained per source
• merging to main follows the repository's Production deployment workflow for both web and API; deployment health remains a separate verification gate

Linear: ANY-1

[linear-code]

ANY-1