fix(circuit-breaker): address CodeRabbit review feedback

Aligns error detection patterns across all implementations and improves
test coverage based on CodeRabbit's critical and major findings.

Changes:
1. CRITICAL: Align lib/response_analyzer.sh pattern with ralph_loop.sh
   - Changed Stage 1 filter from '"[^"]*\(error\|failed\)"[^"]*":' to '"[^"]*error[^"]*":'
   - Removed bare 'cannot' and 'unable to' from Stage 2 (prevent false positives in prose)
   - Both files now use identical patterns for consistency

2. MAJOR: Improved test coverage
   - Renamed test 10 from "Cannot/unable in error context" to "Error prefix with descriptive message"
   - Added test 10a to validate bare "cannot/unable" DON'T trigger false positives
   - Now testing 13 scenarios (was 12)

3. MINOR: Added comprehensive test strategy documentation
   - Header comments explain two-stage filtering approach
   - Documents pattern consistency requirement
   - Lists all 13 test scenarios and their purpose

Test results:
✓ All 13 tests passing
✓ Pattern consistency validated across ralph_loop.sh and lib/response_analyzer.sh
✓ False positive scenarios properly excluded

Addresses CodeRabbit review comments:
- r2655862688 (Critical pattern inconsistency)
- r2655862689 (Major test coverage gap)
- r2655862690 (Minor misleading test name)

lib/response_analyzer.sh

@@ -90,10 +90,11 @@ analyze_response() {
 
     # 4. Detect stuck/error loops
     # Use two-stage filtering to avoid counting JSON field names as errors
-    # Stage 1: Filter out JSON field patterns
-    # Stage 2: Count actual error messages (avoid type annotations like "error: Error")
-    error_count=$(grep -v '"[^"]*\(error\|failed\)"[^"]*":' "$output_file" 2>/dev/null | \
-                  grep -cE '(^Error:|^ERROR:|^error:|\]: error|Link: error|Error occurred|failed with error|[Ee]xception|Fatal|FATAL|cannot|unable to)' \
+    # Stage 1: Filter out JSON field patterns like "is_error": false
+    # Stage 2: Count actual error messages in specific contexts
+    # Pattern aligned with ralph_loop.sh to ensure consistent behavior
+    error_count=$(grep -v '"[^"]*error[^"]*":' "$output_file" 2>/dev/null | \
+                  grep -cE '(^Error:|^ERROR:|^error:|\]: error|Link: error|Error occurred|failed with error|[Ee]xception|Fatal|FATAL)' \
                   2>/dev/null || echo "0")
     error_count=$(echo "$error_count" | tr -d '[:space:]')
     error_count=${error_count:-0}