test(unit): guarantee mock/env cleanup in SEARCH_USER_AGENT override tests

Wrap the three instance-side override tests in try/finally so fetchMocker and
envManager are always restored even if an assertion or awaited call throws —
matching the pattern the FEAT-050 url-reader tests already use. Addresses
Copilot review feedback on PR #150.

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

Author: ihor-sokoliuk

__tests__/unit/instance-info.test.ts

@@ -474,13 +474,15 @@ async function runTests() {
       return createMockFetch({ json: makeConfig() })(url, options);
     });
 
-    await fetchInstanceInfo(mockServer as any);
-
-    const headers = getCapturedOptions()?.headers as Record<string, string>;
-    assert.equal(headers?.['user-agent'], 'SearchBot/2.0');
-
-    fetchMocker.restore();
-    envManager.restore();
+    try {
+      await fetchInstanceInfo(mockServer as any);
+
+      const headers = getCapturedOptions()?.headers as Record<string, string>;
+      assert.equal(headers?.['user-agent'], 'SearchBot/2.0');
+    } finally {
+      fetchMocker.restore();
+      envManager.restore();
+    }
   }, results);
 
   await testFunction('config request omits User-Agent header when USER_AGENT is unset', async () => {

__tests__/unit/search.test.ts

@@ -867,17 +867,19 @@ async function runTests() {
     });
 
     try {
-      await performWebSearch(mockServer as any, 'test query');
-    } catch {
-      // expected
-    }
-
-    const options = getCapturedOptions();
-    const headers = options?.headers as Record<string, string>;
-    assert.equal(headers?.['User-Agent'], 'SearchBot/2.0');
+      try {
+        await performWebSearch(mockServer as any, 'test query');
+      } catch {
+        // expected
+      }
 
-    fetchMocker.restore();
-    envManager.restore();
+      const options = getCapturedOptions();
+      const headers = options?.headers as Record<string, string>;
+      assert.equal(headers?.['User-Agent'], 'SearchBot/2.0');
+    } finally {
+      fetchMocker.restore();
+      envManager.restore();
+    }
   }, results);
 
   await testFunction('User-Agent header absent when USER_AGENT env var not set', async () => {

__tests__/unit/suggestions.test.ts

@@ -203,13 +203,15 @@ async function runTests() {
       return createMockFetch({ json: ['type', ['typescript']] })(url, options);
     });
 
-    await performSearchSuggestions(mockServer as any, 'type');
-
-    const headers = getCapturedOptions()?.headers as Record<string, string>;
-    assert.equal(headers?.['user-agent'], 'SearchBot/2.0');
-
-    fetchMocker.restore();
-    envManager.restore();
+    try {
+      await performSearchSuggestions(mockServer as any, 'type');
+
+      const headers = getCapturedOptions()?.headers as Record<string, string>;
+      assert.equal(headers?.['user-agent'], 'SearchBot/2.0');
+    } finally {
+      fetchMocker.restore();
+      envManager.restore();
+    }
   }, results);
 
   await testFunction('autocompleter request omits User-Agent header when USER_AGENT is unset', async () => {