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>

hooks/gsd-check-update.js

@@ -65,9 +65,10 @@ const child = spawn(process.execPath, ['-e', `
   } catch (e) {}
 
   // Check for stale hooks — compare hook version headers against installed VERSION
+  // Hooks live inside get-shit-done/hooks/, not configDir/hooks/
   let staleHooks = [];
   if (configDir) {
-    const hooksDir = path.join(configDir, 'hooks');
+    const hooksDir = path.join(configDir, 'get-shit-done', 'hooks');
     try {
       if (fs.existsSync(hooksDir)) {
         const hookFiles = fs.readdirSync(hooksDir).filter(f => f.startsWith('gsd-') && f.endsWith('.js'));