docs(claude-md): add Memory hygiene section

CLAUDE.md

@@ -17,6 +17,17 @@ This file is read by Claude Code (and other agents that respect `CLAUDE.md`). Ke
 - Default to no `#` comments. Add one only when the WHY is non-obvious.
 - Test names carry scenarios (`test_<subject>_<scenario>_<expectation>`); per-test docstrings stay rare.
 
+## Memory hygiene
+
+Auto-memory grows monotonically without a forcing function. These rules curb drift between sessions. They apply to `~/.claude/projects/-Users-dgursoy-Documents-Github-cora/memory/`.
+
+- Before creating a new memo, grep MEMORY.md for the topic; prefer edit-in-place over a new file.
+- When tagging a memo SUPERSEDED, move its index entry to `## Reference` in the same edit.
+- After a memo's content reaches SHIPPED and the work has been on main for 30+ days, demote its index entry to `## Reference`.
+- Any index description containing a count, phase tag, or date older than 7 days requires a Read of the underlying file before quoting in chat.
+- Mutable phase status does not belong in index descriptions; the index carries the durable claim, the file carries the status.
+- Memo files over ~300 lines: split into 2-3 sibling files linked from the first.
+
 ## Commits
 
 One-line subject, body explains WHY. Recent commits set the tone — `git log --oneline -10`.