Stack 2 of 7 for the research child-document redesign. Builds on #128.

Adds the restricted-dialect research reference, editor slash-command composer and inline status card, durable request creation/retry/cancellation storage and routes, and the browser request store that restores polling and exact request identity across remounts. This includes the preserved React Strict Mode cleanup recovery fix.

This layer preserves the stack-1 private Research Workspace flow alongside inline requests. It does not include child-document navigation UI or later research workspace redesign work.

Verification: - bun run fix: 0 warnings, 0 errors - Focused research, navigation, dialect, and editor tests: 110 passed - Research Workspace E2E: 6 passed - PostgreSQL contract: 58 passed against the disposable db-e2e service - bun test: 1,331 passed; 2 PostgreSQL skips - bun run types - bun run ci - git diff --check

Environment-only reruns: - The full bun test command was run outside the managed bind sandbox because its socket tests require ephemeral loopback listeners; 1,331 passed and 2 PostgreSQL tests skipped. - PostgreSQL contracts were run outside the network sandbox against the disposable db-e2e service on port 5433; 58 passed. - The focused E2E suite was run outside the sandbox because it requires Docker and local application ports; 6 passed.