fix(circuit-breaker): fix multi-line error matching in detect_stuck_loop

Addresses CodeRabbit outside diff range comment on lines 268-283:

CRITICAL BUG:
The detect_stuck_loop function had a multi-line string handling bug where
only the first error line was checked against historical outputs when
multiple distinct errors were present.

Problem:
  grep -q "$current_errors" file.log
  # When $current_errors has multiple lines, grep only matches first line

Impact:
Stuck loops with multiple recurring errors would not be detected correctly,
potentially allowing Ralph to continue running despite being genuinely stuck.

Fix:
Changed from simple grep to nested loop checking:
- For each historical output file
  - For each error line in current output
    - ALL error lines must appear in that file
- Only returns "stuck" if ALL files contain ALL current errors

Used grep -qF for literal fixed-string matching (not regex) to avoid
edge cases with special characters in error messages.

Test Coverage:
Added 2 new test scenarios (7 → 9 total tests):

Test 8: Multiple distinct errors where ALL repeat across history
  Current: Error: Build failed + Fatal: DB lost + Exception: NPE
  History: All 3 files contain all 3 errors
  Expected: Stuck detected ✅

Test 9: Multiple errors where only some repeat
  Current: Error: Build failed + Fatal: DB lost
  History: Only first error appears consistently
  Expected: Not stuck ✅

All existing tests continue to pass, validating backward compatibility.

Test results:
✓ Error detection tests: 13/13 passing
✓ Stuck loop tests: 9/9 passing (was 7/7)
✓ Total: 22/22 tests passing

This ensures detect_stuck_loop correctly handles the real-world scenario
where Ralph gets stuck on multiple simultaneous recurring errors.

Addresses CodeRabbit review comment:
- Outside diff range (lines 268-283): Multi-line error matching bug

lib/response_analyzer.sh

@@ -274,15 +274,26 @@ detect_stuck_loop() {
     fi
 
     # Check if same errors appear in all recent outputs
-    local stuck_count=0
+    # For multi-line errors, verify ALL error lines appear in ALL history files
+    local all_files_match=true
     while IFS= read -r output_file; do
-        if grep -q "$current_errors" "$output_file" 2>/dev/null; then
-            ((stuck_count++))
+        local file_matches_all=true
+        while IFS= read -r error_line; do
+            # Use -F for literal fixed-string matching (not regex)
+            if ! grep -qF "$error_line" "$output_file" 2>/dev/null; then
+                file_matches_all=false
+                break
+            fi
+        done <<< "$current_errors"
+
+        if [[ "$file_matches_all" != "true" ]]; then
+            all_files_match=false
+            break
         fi
     done <<< "$recent_outputs"
 
-    if [[ $stuck_count -ge 3 ]]; then
-        return 0  # Stuck on same error
+    if [[ "$all_files_match" == "true" ]]; then
+        return 0  # Stuck on same error(s)
     else
         return 1  # Making progress or different errors
     fi