calendar-invite: add VALARM reminder, fix terminology, remove dead code

- Add 1-day reminder (VALARM) to all sent invites
- Fix datetime.utcnow() deprecation → datetime.now(timezone.utc)
- Rename "message ID" → "envelope ID" in SKILL.md for consistency
- Remove unused _himalaya() and _himalaya_with_account() helpers

skills/calendar-invite/SKILL.md

@@ -27,7 +27,7 @@ Calendar invites are outbound emails. Follow the workspace email rules:
 
 ## Owner Auto-Attendee
 
-When sending invites, `mail@luyx.org` (owner's SimpleLogin alias) is **always added as an attendee automatically**. This ensures the owner receives every invite and can Accept/Decline from their own email client. No need to include it in `--to` — it's added by the script.
+When sending invites, `mail@luyx.org` (owner's SimpleLogin alias) is **always added as an attendee automatically**. All invites include a **1-day reminder** (VALARM) by default. This ensures the owner receives every invite and can Accept/Decline from their own email client. No need to include it in `--to` — it's added by the script.
 
 When accepting or tentatively accepting a received invite, the original invite is **automatically forwarded to `mail@luyx.org`** so the event lands on the owner's calendar too.
 
@@ -113,7 +113,7 @@ $SKILL_DIR/scripts/calendar-invite.sh send \
 ## Replying to Invites
 
 ```bash
-# Accept by himalaya message ID
+# Accept by himalaya envelope ID
 $SKILL_DIR/scripts/calendar-invite.sh reply \
   --envelope-id 42 \
   --action accept
@@ -135,7 +135,7 @@ $SKILL_DIR/scripts/calendar-invite.sh reply \
 | Flag            | Required | Description                                         |
 |-----------------|----------|-----------------------------------------------------|
 | `--action`      | Yes      | `accept`, `decline`, or `tentative`                  |
-| `--envelope-id`  | *        | Himalaya message ID containing the .ics attachment   |
+| `--envelope-id`  | *        | Himalaya envelope ID containing the .ics attachment  |
 | `--ics-file`    | *        | Path to an .ics file (alternative to `--envelope-id`) |
 | `--from`        | No       | Your email (default: `youlu@luyanxin.com`)           |
 | `--account`     | No       | Himalaya account name                                |

skills/calendar-invite/scripts/calendar_invite.py

@@ -14,14 +14,14 @@ import argparse
 import subprocess
 import sys
 import uuid
-from datetime import datetime
+from datetime import datetime, timedelta, timezone
 from pathlib import Path
 
 from email.mime.base import MIMEBase
 from email.mime.multipart import MIMEMultipart
 from email.mime.text import MIMEText
 
-from icalendar import Calendar, Event, vCalAddress, vText
+from icalendar import Alarm, Calendar, Event, vCalAddress, vText
 
 # ---------------------------------------------------------------------------
 # Config
@@ -38,24 +38,6 @@ PRODID = "-//OpenClaw//CalendarInvite//EN"
 # Helpers
 # ---------------------------------------------------------------------------
 
-def _himalaya(*args):
-    """Run a himalaya command and return stdout."""
-    result = subprocess.run(
-        ["himalaya", *args],
-        capture_output=True, text=True, check=True,
-    )
-    return result.stdout
-
-
-def _himalaya_with_account(account, *args):
-    """Run a himalaya command with optional account flag."""
-    cmd = ["himalaya"]
-    if account:
-        cmd += ["--account", account]
-    cmd += list(args)
-    result = subprocess.run(cmd, capture_output=True, text=True, check=True)
-    return result.stdout
-
 
 def _sync_calendar():
     """Sync local calendar to CalDAV server via vdirsyncer."""
@@ -123,7 +105,7 @@ def cmd_send(args):
 
     event = Event()
     event.add("uid", uid)
-    event.add("dtstamp", datetime.utcnow())
+    event.add("dtstamp", datetime.now(timezone.utc))
     event.add("dtstart", start, parameters={"TZID": args.timezone})
     event.add("dtend", end, parameters={"TZID": args.timezone})
     event.add("summary", args.summary)
@@ -151,6 +133,13 @@ def cmd_send(args):
             "RSVP": "TRUE",
         })
 
+    # 1-day reminder
+    alarm = Alarm()
+    alarm.add("action", "DISPLAY")
+    alarm.add("description", f"Reminder: {args.summary}")
+    alarm.add("trigger", timedelta(days=-1))
+    event.add_component(alarm)
+
     cal.add_component(event)
     ics_bytes = cal.to_ical()
 
@@ -286,7 +275,7 @@ def cmd_reply(args):
 
     reply_event = Event()
     reply_event.add("uid", uid)
-    reply_event.add("dtstamp", datetime.utcnow())
+    reply_event.add("dtstamp", datetime.now(timezone.utc))
 
     # Copy timing from original
     if original_event.get("dtstart"):