feat(cron): add one-time 'at' schedule to skill docs and show timezone in system prompt

nanobot/agent/context.py

@@ -73,7 +73,9 @@ Skills with available="false" need dependencies installed first - you can try in
     def _get_identity(self) -> str:
         """Get the core identity section."""
         from datetime import datetime
+        import time as _time
         now = datetime.now().strftime("%Y-%m-%d %H:%M (%A)")
+        tz = _time.strftime("%Z") or "UTC"
         workspace_path = str(self.workspace.expanduser().resolve())
         system = platform.system()
         runtime = f"{'macOS' if system == 'Darwin' else system} {platform.machine()}, Python {platform.python_version()}"
@@ -88,7 +90,7 @@ You are nanobot, a helpful AI assistant. You have access to tools that allow you
 - Spawn subagents for complex background tasks
 
 ## Current Time
-{now}
+{now} ({tz})
 
 ## Runtime
 {runtime}

nanobot/skills/cron/SKILL.md

@@ -7,10 +7,11 @@ description: Schedule reminders and recurring tasks.
 
 Use the `cron` tool to schedule reminders or recurring tasks.
 
-## Two Modes
+## Three Modes
 
 1. **Reminder** - message is sent directly to user
 2. **Task** - message is a task description, agent executes and sends result
+3. **One-time** - runs once at a specific time, then auto-deletes
 
 ## Examples
 
@@ -24,6 +25,11 @@ Dynamic task (agent executes each time):
 cron(action="add", message="Check HKUDS/nanobot GitHub stars and report", every_seconds=600)
 ```
 
+One-time scheduled task (compute ISO datetime from current time):
+```
+cron(action="add", message="Remind me about the meeting", at="<ISO datetime>")
+```
+
 List/remove:
 ```
 cron(action="list")
@@ -38,3 +44,4 @@ cron(action="remove", job_id="abc123")
 | every hour | every_seconds: 3600 |
 | every day at 8am | cron_expr: "0 8 * * *" |
 | weekdays at 5pm | cron_expr: "0 17 * * 1-5" |
+| at a specific time | at: ISO datetime string (compute from current time) |