Sprint 5S: project truth synchronization after Gmail auth hardening

[samrusani]

Summary

• synchronize architecture, roadmap, and handoff truth artifacts with the accepted repo state through Sprint 5R
• correct stale Sprint 5J-era statements and document the shipped narrow document-ingestion and Gmail auth seams
• keep the sprint documentation-only with no runtime, schema, API, connector-breadth, runner, or UI changes

Verification

• ./.venv/bin/python -m pytest tests/unit
• ./.venv/bin/python -m pytest tests/integration