fix: use word boundaries in grep patterns to prevent false positives (#100)

Address PR #86 review feedback from Gemini:
- Line 145: replace 'grep -i error|fail|exception' with grep -E -i '\b(error|fail|exception)'
- Line 224: replace 'grep -i ERROR|WARNING' with grep -E -i '\b(ERROR|WARNING)\b'

Using \b word boundaries prevents substring matches (e.g. 'exception' in
'unexceptional') and removes the unnecessary cat pipe (UUOC).

Closes #94

.agents/error-checking-feedback-loops.md

@@ -142,7 +142,7 @@ npm run test:playground:multisite
 2. **Analyze Output for Errors**:
 
    ```bash
-   grep -i 'error\|fail\|exception' test-output.log
+   grep -E -i '\b(error|fail|exception)' test-output.log
    ```
 
 3. **Parse Structured Test Results** (if available):
@@ -221,7 +221,7 @@ npm run lint:css
 2. **Analyze Output for Errors**:
 
    ```bash
-   grep -i 'ERROR\|WARNING' phpcs-output.log
+   grep -E -i '\b(ERROR|WARNING)\b' phpcs-output.log
    ```
 
 3. **Automatically Fix Issues** (when possible):