fix(delegate-job): unify .env loading in Python scripts (FW-04) + trap agent bootstrap errors (FW-06)

FW-04: mqtt_common.py now loads .env at module import via _load_dotenv().
  Walks up from script dir to find workspace .env, sets vars not already
  in os.environ (OS env takes precedence). Uses stdlib only — no
  python-dotenv dependency.

FW-06: bash wrapper sets trap EXIT before tmux new-session to publish
  error event if agent bootstrap fails (non-zero exit). Trap is cleared
  after successful session creation. Only active when job_id is set.

skills/tmux-agent-orchestrate-delegate-job/scripts/mqtt_common.py

@@ -33,6 +33,40 @@ import paho.mqtt.client as mqtt
 
 logger = logging.getLogger("delegate_job.mqtt_common")
 
+def _load_dotenv(workspace_dir: str = None) -> None:
+    """Load .env file from workspace if it exists and env var not already set.
+    
+    This ensures Python scripts get the same env vars as the shell wrapper
+    scripts that source .env. Only sets vars that are not already in os.environ
+    (i.e. OS env takes precedence over .env file).
+    """
+    import os
+    if workspace_dir is None:
+        # Walk up from this script to find workspace root
+        d = os.path.dirname(os.path.abspath(__file__))
+        for _ in range(5):
+            if os.path.isfile(os.path.join(d, ".env")):
+                break
+            d = os.path.dirname(d)
+    else:
+        d = workspace_dir
+    env_path = os.path.join(d, ".env")
+    if not os.path.isfile(env_path):
+        return
+    with open(env_path, "r") as f:
+        for line in f:
+            line = line.strip()
+            if not line or line.startswith("#"):
+                continue
+            if "=" in line:
+                key, _, val = line.partition("=")
+                key = key.strip()
+                val = val.strip().strip('"').strip("'")
+                if key and key not in os.environ:
+                    os.environ[key] = val
+
+_load_dotenv()
+
 # --------------------------------------------------------------------------
 # Constants
 # --------------------------------------------------------------------------