fix: stale hook detection checks wrong directory path

gsd-check-update.js looked for hooks in configDir/hooks/ (e.g.,
~/.claude/hooks/) but the installer writes hooks to
configDir/get-shit-done/hooks/. This mismatch caused false stale
hook warnings that persisted even after updating.

Also clears the update cache during install so the next session
re-evaluates hook versions with the correct path.

Closes #1249

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tests/core.test.cjs

@@ -967,6 +967,26 @@ describe('stale hook filter', () => {
   });
 });
 
+// ─── stale hook path regression (#1249) ──────────────────────────────────────
+
+describe('stale hook path', () => {
+  test('gsd-check-update.js checks get-shit-done/hooks/ not configDir/hooks/', () => {
+    const content = fs.readFileSync(
+      path.join(__dirname, '..', 'hooks', 'gsd-check-update.js'), 'utf-8'
+    );
+    assert.ok(
+      content.includes("path.join(configDir, 'get-shit-done', 'hooks')"),
+      'stale hook check must look in configDir/get-shit-done/hooks/, not configDir/hooks/'
+    );
+    assert.ok(
+      !content.includes("path.join(configDir, 'hooks')") ||
+      content.indexOf("path.join(configDir, 'get-shit-done', 'hooks')") <
+      content.indexOf("path.join(configDir, 'hooks')") + 100, // allow the old pattern only if corrected version exists first
+      'should not use the wrong hooks path'
+    );
+  });
+});
+
 // ─── resolveWorktreeRoot ─────────────────────────────────────────────────────
 
 describe('resolveWorktreeRoot', () => {