chore(gitignore): block .claude/HANDOFF_* and .claude/CODEMAP_* patterns

Follow-up to the previous commit that removed two leaked handoff
files from `.claude/`. The actual removal landed, but the
`.gitignore` rules that would prevent a future accidental re-add
were left in the working tree by mistake.

Adds:

  .claude/HANDOFF_*
  .claude/CODEMAP_*
  .claude/handoff_*  (case-insensitive belt-and-suspenders)
  .claude/codemap_*

so `git add .claude/HANDOFF_v0.8.32_*` etc. is silently dropped at
add time instead of slipping through review.

Verified with `git check-ignore`:
  .gitignore:89:.claude/handoff_*  .claude/HANDOFF_test_scratch.md

.gitignore

@@ -79,5 +79,15 @@ apps/
 .claude/*.local.md
 .claude/*.local.json
 
+# Maintainer handoff + codemap notes are working-state, not user-facing
+# artifacts. They've leaked into the public repo via .claude/ in the past
+# (HANDOFF_v0.8.28, CODEMAP_v0.8.25) — those files now live under
+# .private/handoffs/ instead. Block the patterns here so a future accidental
+# add doesn't silently land on main.
+.claude/HANDOFF_*
+.claude/CODEMAP_*
+.claude/handoff_*
+.claude/codemap_*
+
 # Maintainer-internal design notes (trade-secret material, never published)
 .private/