feat(tier4): Add patch generation for auto-patching

- Add TIER4_PATCH_PROMPT to mma_prompts.py with unified diff format
- Add run_tier4_patch_generation function to ai_client.py
- Import mma_prompts in ai_client.py
- Add unit tests for patch generation

src/mma_prompts.py

@@ -153,3 +153,28 @@ PROMPTS: Dict[str, str] = {
  "tier2_track_finalization": TIER2_TRACK_FINALIZATION,
  "tier2_contract_first": TIER2_CONTRACT_FIRST,
 }
+
+TIER4_PATCH_PROMPT: str = """You are a Tier 4 QA Agent specializing in error analysis and patch generation.
+When a test or command fails, analyze the error and generate a unified diff patch to fix it.
+
+OUTPUT FORMAT: Unified diff format (diff -u)
+```
+--- a/path/to/file.py
++++ b/path/to/file.py
+@@ -start,count +start,count @@
+ context line
+-removed line
++added line
+ context line
+```
+
+RULES:
+1. Use "--- a/" and "+++ b/" prefixes with the actual file path
+2. Include sufficient context lines (3 above/below minimum)
+3. Use @@ -X,Y +X,Y @@ format for hunk headers
+4. Only include changes necessary to fix the error
+5. If multiple files need changes, include each in the patch
+6. Output ONLY the unified diff - no explanations, no markdown code blocks
+
+Analyze this error and generate the patch:
+"""