fix(cron): inject runtime env hint into cron system prompt (#378)

The agent doesn't know its execution environment. When running on
cloud, it blindly attempts localhost calls from the prompt.

Add _build_cron_env_hint() that generates a [CRON ENV] block:
- LOCAL: 'localhost access, SSH, local services available'
- CLOUD: 'NO localhost access, NO SSH, NO local services.
  If instructions reference localhost/Ollama/SSH, report the
  limitation instead of attempting.'

Injected into the prompt after resolve_turn_route() so the agent
knows its environment before executing any instructions.

Closes #378

cron/scheduler.py

@@ -643,6 +643,36 @@ def _build_job_prompt(job: dict) -> str:
     return "\n".join(parts)
 
 
+def _build_cron_env_hint(base_url: str, provider: str, disabled_toolsets: list) -> str:
+    """Build a runtime environment hint block for the cron system prompt.
+
+    Tells the agent about its execution environment so it can self-adjust
+    when instructions reference capabilities it doesn't have. (#378)
+    """
+    try:
+        from agent.model_metadata import is_local_endpoint
+    except ImportError:
+        is_local_endpoint = lambda _: False
+
+    is_local = is_local_endpoint(base_url or "")
+
+    parts = ["[CRON ENV:"]
+
+    if is_local:
+        parts.append(f"Runtime: LOCAL ({provider or 'local'} at {base_url or 'localhost'})")
+        parts.append("Capabilities: localhost access, SSH, local services available.")
+    else:
+        parts.append(f"Runtime: CLOUD ({provider or 'cloud'} at {base_url or 'remote'})")
+        parts.append("Capabilities: NO localhost access, NO SSH, NO local services.")
+        parts.append("If instructions reference localhost/Ollama/SSH, report the limitation instead of attempting.")
+
+    if disabled_toolsets:
+        parts.append(f"Disabled tools: {', '.join(disabled_toolsets)}.")
+
+    parts.append("]")
+    return " ".join(parts)
+
+
 def run_job(job: dict) -> tuple[bool, str, str, Optional[str]]:
     """
     Execute a single cron job.