Adds a 'Handoff: Remaining Drifted Docs' section listing:
- 4 already-fixed stale refs found proactively outside the original
4-commits scope (Readme, 2 reports, guide_tools, 2 source docstrings)
- 9 categories of remaining work (A through I) with file lists, LOC,
and which docs reference each bucket
- A recommended 3-track decomposition that fits each category in
one agent context frame
- The 4 most-common drift patterns I encountered (thread counts,
line numbers, removed-class claims, schema fields)
The next agent can pick up directly from this section without
re-doing the audit I already completed.