feat: add /goal command for durable multi-turn objectives

- /goal set|status|checkpoint|pause|resume|clear intercept in main.py
- GOAL.md injected into system prompt when active (prompt_builder.py)
- Goal context added to heartbeat for autonomous progress

agentclaw/app/agent_claw_main/prompt_builder.py

@@ -46,6 +46,16 @@ def _get_base_prompt(actor_id: str = '') -> str:
     s3 = boto3.client('s3')
     parts = []
 
+    # Inject active goal at the top of context
+    try:
+        obj = s3.get_object(Bucket=bucket, Key='GOAL.md')
+        goal_content = obj['Body'].read().decode('utf-8')
+        if '**Status:** active' in goal_content:
+            parts.append(f'## Active Goal\n{goal_content}')
+            print(f'[prompt_builder] Injected GOAL.md ({len(goal_content)} bytes)')
+    except Exception:
+        pass
+
     for fname in ['SOUL.md', 'STATUS.md']:
         try:
             obj = s3.get_object(Bucket=bucket, Key=fname)