Preserve detector extension mappings

Keep unmanaged detector fields when ignore-file updates the canonical detector configuration. Add a regression covering existing extension mappings.\n\nAI assistance: Codex implemented and validated this change under maintainer authorization.

skill/scripts/hook-admin.mjs

@@ -240,10 +240,14 @@ function writeDetectorConfig(cwd, detectorConfig, opts = {}) {
   const existingRaw = readRawConfigFile(filePath).raw;
   const existing = existingRaw && typeof existingRaw === 'object' && !Array.isArray(existingRaw) ? existingRaw : {};
   const nextHook = stripDetectorKeys(hookSection(existing));
-  const existingDetector = mergeDetectorConfig(detectorSection(existing));
+  const existingDetectorSection = detectorSection(existing) || {};
+  const existingDetector = mergeDetectorConfig(existingDetectorSection);
   const next = {
     ...existing,
-    detector: mergeDetectorConfig(detectorConfig, existingDetector),
+    detector: {
+      ...existingDetectorSection,
+      ...mergeDetectorConfig(detectorConfig, existingDetector),
+    },
   };
   if (Object.keys(nextHook).length > 0) next.hook = nextHook;
   else delete next.hook;

tests/hook.test.mjs

@@ -1058,9 +1058,15 @@ describe('hook-admin.mjs', () => {
     fs.mkdirSync(path.dirname(file), { recursive: true });
     fs.writeFileSync(file, '<div style="border-left: 4px solid #7c3aed; border-radius: 16px; padding: 16px;">Card</div>');
 
+    fs.mkdirSync(path.dirname(getConfigPath(cwd)), { recursive: true });
+    fs.writeFileSync(getConfigPath(cwd), JSON.stringify({
+      detector: { extensions: [{ ext: '.blade.php', engine: 'html' }] },
+    }));
+
     runAdmin(['ignore-file', 'src/ConfirmedCard.html']);
 
     const shared = JSON.parse(fs.readFileSync(getConfigPath(cwd), 'utf-8')).detector;
+    assert.deepEqual(shared.extensions, [{ ext: '.blade.php', engine: 'html' }]);
     assert.deepEqual(shared.ignoreFiles, ['src/ConfirmedCard.html']);
 
     const r = await runHook({