fix(plugin): an early-exiting head no longer voids its own output under pipefail (#4042)

In a repo where 3,000 files define `slug`, scribe_local_dups printed
nothing; with 3 files it printed the duplicate line. Every hook runs under
`set -uo pipefail`, and `hits=$(git grep -l … | head -4) || hits=""` lost
head's four lines whenever git grep was still writing when head exited. That
is a SIGPIPE, the substitution fails, and the outer fallback wipes the result.
So the by-name duplicate arm went silent for exactly the most-duplicated
names. Found while fixing the same trap in the new Stop hook (#4041).

- The fallback moves inside the substitution, `$(… | head -N || true)`, at all
  five sites: scribe_defs.sh (local dups), scribe_prior_art.sh (names,
  old_first, shapes) and scribe_after_write.sh (names). A real upstream
  failure still yields empty output.
- check_plugin gains a known-bad pattern for the shape, so no hook can bring
  it back.
- Tests: the real function against a 3,000-file repo (past the pipe buffer),
  and the pattern shown to flag the old shape and pass the fix. Plugin
  version minted.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

plugin/.claude-plugin/plugin.json

@@ -1,7 +1,7 @@
 {
   "name": "scribe",
   "description": "Scribe for Claude Code: connects the scribe MCP server, adds the hooks that deliver live project state and relevant records at the right moment, ships the shared client-neutral Scribe skills (using-scribe, writing-plans, reporting-back, systematic-debugging, verification, brainstorming, reusing-code, shape-accounting), and syncs your saved Scribe Processes as skills (/scribe:sync).",
-  "version": "2026.09.14.2237",
+  "version": "2026.09.14.2254",
   "author": {
     "name": "Bryan Van Deusen"
   },