fix(lint): flag release-relevant paths retired since the last tag

Coverage was derived from the worktree alone, so the -d guard on a
hook's bundled assets/ tree meant deleting the whole tree removed it
from the pathspec instead of flagging it — the gate stayed silent
about a change that breaks every consumer at the next rev:.

The path set is now derived twice, from the worktree manifest and from
the manifest at $LAST_TAG, then unioned. A path the tag exposed but
HEAD no longer does is a removal pinned consumers must be told about;
a path only HEAD exposes is new contract surface. Both need flagging.

Fails closed on an unreadable tagged tree (shallow clone), and treats
a readable root tree with no manifest as "added since the tag".

tokens[0] needed no exit-code fix — it carries no existence guard, so
both deletion cases already exited non-zero. What was wrong was the
reporting: a fully retired hook could no longer be named in the
failure message. The tagged manifest fixes that.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MCQ648fLSFXPHGZdQ8gn58

tests/test-check-release-needed.sh

@@ -211,6 +211,63 @@ else
   fail "invented a bogus assets/ path for a hook script with no bundled tree"
 fi
 
+# --- 12. Deleting a hook's entire bundled assets/ tree is release-relevant ---
+# The worktree-only derivation guarded the assets/ path on the directory still
+# existing, so wiping the whole tree removed the path from the pathspec instead
+# of diffing it: the single most consumer-breaking change possible diffed clean.
+# The path list therefore has to be unioned with what $LAST_TAG exposed.
+echo ""
+echo "--- exits 1 when a hook's entire bundled assets/ tree was deleted since the tag ---"
+FIXTURE12="$(make_tagged_fixture)"; track "$FIXTURE12"
+rm -rf "${FIXTURE12:?}/$HOOK_DIR/assets"
+(cd "$FIXTURE12" && git add -A && git commit -q -m "delete the whole bundled assets tree")
+OUT12=$(run_check "$FIXTURE12" "refs/heads/main" || true)
+if echo "$OUT12" | grep -q "assets/vale/.vale.ini"; then
+  pass "flags a wholesale deletion of a hook's bundled assets/ tree"
+else
+  fail "a hook's entire bundled assets/ tree vanished since the tag without demanding a release"
+fi
+
+# --- 13. A hook script deleted while its manifest entry survives is flagged ---
+# Characterisation test, not a bug fix: tokens[0] is added to the pathspec
+# unconditionally (no existence guard), so this case was already covered. It is
+# pinned here so the tagged-tree union can't accidentally introduce an existence
+# guard on tokens[0] and reopen the hole its assets/ sibling had.
+echo ""
+echo "--- exits 1 when a hook script was deleted but its manifest entry remains ---"
+FIXTURE13="$(make_tagged_fixture)"; track "$FIXTURE13"
+rm -f "$FIXTURE13/$HOOK_DIR/scripts/vale-wrap.sh"
+(cd "$FIXTURE13" && git add -A && git commit -q -m "delete a hook script, keep its manifest entry")
+OUT13=$(run_check "$FIXTURE13" "refs/heads/main" || true)
+if echo "$OUT13" | grep -q "vale-wrap.sh"; then
+  pass "flags a hook script deleted out from under a surviving manifest entry"
+else
+  fail "a manifest entry's script vanished since the tag without demanding a release"
+fi
+
+# --- 14. Retiring a whole hook names what the tag exposed, not just the manifest ---
+# Removing the entry and everything it shipped changes $HOOKS_MANIFEST, so the
+# gate fires either way — but a derivation that only reads the current manifest
+# can no longer name the retired script or its assets, and the failure message
+# understates the breakage to consumers pinned at the old rev. The tagged
+# manifest is what makes those paths reportable.
+echo ""
+echo "--- names the retired hook's own paths when an entry and its files are removed together ---"
+FIXTURE14="$(make_tagged_fixture)"; track "$FIXTURE14"
+cat > "$FIXTURE14/.pre-commit-hooks.yaml" <<'EOF'
+-   id: fake-size-check
+    entry: scripts/skill-size-check.sh
+    language: script
+EOF
+rm -rf "${FIXTURE14:?}/$HOOK_DIR"
+(cd "$FIXTURE14" && git add -A && git commit -q -m "retire the vale hook entirely")
+OUT14=$(run_check "$FIXTURE14" "refs/heads/main" || true)
+if echo "$OUT14" | grep -q "vale-wrap.sh" && echo "$OUT14" | grep -q "assets/vale/.vale.ini"; then
+  pass "names the retired hook's script and bundled assets, not just the manifest edit"
+else
+  fail "reported only the manifest change and hid which shipped paths the retirement removed"
+fi
+
 echo ""
 echo "Results: $PASS passed, $FAIL failed"
 [[ $FAIL -eq 0 ]]