test: add stress test and PostToolUse preservation tests

- Add stress test for 15 duplicate hooks (verifies O(n) scaling)
- Add test verifying PostToolUse/PreToolCall remain untouched
- Add optional debug logging when duplicates removed (CCS_DEBUG)

Addresses review feedback from PR #452

src/utils/websearch/hook-utils.ts

@@ -48,5 +48,11 @@ export function deduplicateCcsHooks(settings: Record<string, unknown>): boolean
     return false; // Remove subsequent duplicates
   });
 
-  return hooks.PreToolUse.length < originalLength;
+  const newLength = hooks.PreToolUse.length;
+  if (process.env.CCS_DEBUG && newLength < originalLength) {
+    const removedCount = originalLength - newLength;
+    console.error(`Removed ${removedCount} duplicate CCS WebSearch hook(s)`);
+  }
+
+  return newLength < originalLength;
 }

tests/unit/utils/websearch/hook-utils.test.ts

@@ -289,4 +289,83 @@ describe('deduplicateCcsHooks', () => {
     expect(result).toBe(false);
     expect(settings.hooks.PreToolUse).toHaveLength(0);
   });
+
+  test('Stress test: 15 duplicate CCS WebSearch hooks', () => {
+    const ccsHook = {
+      matcher: 'WebSearch',
+      hooks: [
+        {
+          command: 'node /home/user/.ccs/hooks/websearch-transformer/index.js',
+        },
+      ],
+    };
+    const settings = {
+      hooks: {
+        PreToolUse: Array(15).fill(ccsHook),
+      },
+    };
+    const result = deduplicateCcsHooks(settings);
+    expect(result).toBe(true);
+    expect(settings.hooks.PreToolUse).toHaveLength(1);
+    expect(settings.hooks.PreToolUse[0]).toEqual(ccsHook);
+  });
+
+  test('Leaves PostToolUse and PreToolCall untouched', () => {
+    const postToolUseHook1 = {
+      matcher: 'CustomMatcher1',
+      hooks: [{ command: 'custom-command-1' }],
+    };
+    const postToolUseHook2 = {
+      matcher: 'CustomMatcher2',
+      hooks: [{ command: 'custom-command-2' }],
+    };
+    const preToolCallHook = {
+      matcher: 'CustomMatcher3',
+      hooks: [{ command: 'custom-command-3' }],
+    };
+    const settings = {
+      hooks: {
+        PreToolUse: [
+          {
+            matcher: 'WebSearch',
+            hooks: [
+              {
+                command: 'node /path1/.ccs/hooks/websearch-transformer/index.js',
+              },
+            ],
+          },
+          {
+            matcher: 'WebSearch',
+            hooks: [
+              {
+                command: 'node /path2/.ccs/hooks/websearch-transformer/index.js',
+              },
+            ],
+          },
+          {
+            matcher: 'WebSearch',
+            hooks: [
+              {
+                command: 'node /path3/.ccs/hooks/websearch-transformer/index.js',
+              },
+            ],
+          },
+        ],
+        PostToolUse: [postToolUseHook1, postToolUseHook2],
+        PreToolCall: [preToolCallHook],
+      },
+    };
+    const result = deduplicateCcsHooks(settings);
+    expect(result).toBe(true);
+    // PreToolUse should be deduplicated to 1 hook
+    expect(settings.hooks.PreToolUse).toHaveLength(1);
+    expect(settings.hooks.PreToolUse[0].matcher).toBe('WebSearch');
+    // PostToolUse should remain unchanged with 2 hooks
+    expect(settings.hooks.PostToolUse).toHaveLength(2);
+    expect(settings.hooks.PostToolUse[0]).toEqual(postToolUseHook1);
+    expect(settings.hooks.PostToolUse[1]).toEqual(postToolUseHook2);
+    // PreToolCall should remain unchanged with 1 hook
+    expect(settings.hooks.PreToolCall).toHaveLength(1);
+    expect(settings.hooks.PreToolCall[0]).toEqual(preToolCallHook);
+  });
 });