docs(catalog): repo-mailbox selftest checks 374 -> 370, measured at the tag

Same defect as 780f86e, in a number I wrote myself in e9054f8: 374 came from
repo-mailbox's working tree, which has committed past v0.18.0 (board-selftest.sh
is +44 lines there, worth 4 extra checks). The catalog documents what installs.

Measured at the pinned tag, extracted read-only with `git archive v0.18.0` into a
scratch dir (never a checkout in another repo): coord 183 + route 73 + board 114
= 370. CLI scripts stays 8 — scripts/ holds the same 11 *.sh at the tag as at
HEAD, of which 3 are selftests.

Both axes are badge-less, so the gate cannot check either. That is the point:
this is the class that needs a human pass, and it just proved it twice.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RDSiMcgLMpEETwtkc86Nym

README.md

@@ -188,7 +188,7 @@ A local mailbox for coordination between Claude Code sessions in different repos
 - **`board`** — read-only cross-repo attention board: which repos have a live next step, which are blocked and on whom, which owe a reply, and what each costs to move
 - **`route`** — turns four scored traits of the next task into a model/effort row from a closed six-row rubric, with a pasteable startup command and a one-row-cheaper fallback
 
-1 hook · 3 skills · 8 CLI scripts · 374 selftest checks · [Full documentation →](https://git.fromaitochitta.com/open/repo-mailbox)
+1 hook · 3 skills · 8 CLI scripts · 370 selftest checks · [Full documentation →](https://git.fromaitochitta.com/open/repo-mailbox)
 
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