feat(test): validate touchfile dependency paths exist on disk

New guard in touchfiles.test.ts: every non-glob dep path must exist, and every
glob's anchor directory must exist. This is the axis the 181-key two-map sync
discipline never covered — an entry can point at a long-deleted file and
diff-based selection then silently never triggers those tests (the sidebar
trio sat rotted for 48 versions).

First run immediately caught a fourth rotted entry: 'spec authored quality'
referenced test/fixtures/spec/** (directory does not exist) and selected for a
judge test that exists nowhere in the repo. Removed.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

test/helpers/touchfiles.ts

@@ -775,7 +775,6 @@ export const LLM_JUDGE_TOUCHFILES: Record<string, string[]> = {
   'plan-eng-review/SKILL.md sections':    ['plan-eng-review/SKILL.md', 'plan-eng-review/SKILL.md.tmpl'],
 
   // /spec authored-spec quality (paid LLM-judge — periodic-tier).
-  'spec authored quality':                ['spec/SKILL.md', 'spec/SKILL.md.tmpl', 'test/fixtures/spec/**'],
   'plan-design-review/SKILL.md passes':   ['plan-design-review/SKILL.md', 'plan-design-review/SKILL.md.tmpl'],
 
   // Design skills

test/touchfiles.test.ts

@@ -330,3 +330,57 @@ describe('TOUCHFILES completeness', () => {
     }
   });
 });
+
+// --- dependency paths exist on disk ---
+//
+// The axis nobody guarded: a dep-list entry can point at a file that was
+// deleted long ago (browse/src/sidebar-agent.ts sat in three entries for 48
+// versions), and diff-based selection then silently never triggers those
+// tests. Globs are skipped (they describe patterns, not files); every literal
+// path must exist.
+
+describe('touchfile dependency paths exist', () => {
+  const allEntries: Array<[string, string]> = [];
+  for (const [name, deps] of Object.entries(E2E_TOUCHFILES)) {
+    for (const dep of deps) allEntries.push([name, dep]);
+  }
+  for (const [name, deps] of Object.entries(LLM_JUDGE_TOUCHFILES)) {
+    for (const dep of deps) allEntries.push([name, dep]);
+  }
+  for (const dep of GLOBAL_TOUCHFILES) allEntries.push(['(global)', dep]);
+
+  test('every non-glob dependency path exists', () => {
+    const stale = allEntries
+      .filter(([, dep]) => !dep.includes('*'))
+      .filter(([, dep]) => !fs.existsSync(path.join(ROOT, dep)));
+    if (stale.length > 0) {
+      throw new Error(
+        `Touchfile dep lists reference files that do not exist:\n` +
+        stale.map(([name, dep]) => `  ${name} -> ${dep}`).join('\n') +
+        `\nDelete or update these entries in test/helpers/touchfiles.ts — ` +
+        `diff-based selection silently skips tests whose deps are gone.`,
+      );
+    }
+  });
+
+  test('every glob dependency anchors to a directory that exists', () => {
+    // Cheap sanity for globs, two shapes: 'dir/**' (prefix ends with '/')
+    // must have the directory itself; 'dir/file-prefix*.ext' must have the
+    // containing directory. Catches 'deleted-dir/**' rot without a full
+    // filesystem walk; deliberately does not chase file-prefix staleness.
+    const stale = allEntries
+      .filter(([, dep]) => dep.includes('*'))
+      .map(([name, dep]) => {
+        const prefix = dep.split('*')[0];
+        const anchor = prefix.endsWith('/') ? prefix.slice(0, -1) : path.dirname(prefix);
+        return [name, dep, anchor] as const;
+      })
+      .filter(([, , anchor]) => anchor.length > 0 && anchor !== '.' && !fs.existsSync(path.join(ROOT, anchor)));
+    if (stale.length > 0) {
+      throw new Error(
+        `Touchfile glob deps whose anchor directory does not exist:\n` +
+        stale.map(([name, dep]) => `  ${name} -> ${dep}`).join('\n'),
+      );
+    }
+  });
+});