fix(tui): clear stale tool preparation state

[kitlangton]

Fixes #35454

Summary

• reconcile fetched message snapshots against the highest durable event sequence applied locally
• refresh loaded session messages after event-stream reconnects without overwriting newer in-flight state
• make streamed part starts and tool-call transitions idempotent so replay cannot downgrade terminal tools
• cover stale terminal messages, newer live messages, replayed events, and reconnect recovery

Testing

• bun run test -- test/cli/tui/data.test.tsx
• bun typecheck
• repository pre-push typecheck (31 packages)
• bunx prettier --check src/context/data.tsx test/cli/tui/data.test.tsx
• file-scoped oxlint (no errors; existing warnings remain)