feat: clear screen before render so briefing starts at top

No more scrolling up after refresh — the screen clears and
the calendar/summary is always visible at the top.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

briefing

@@ -7,7 +7,7 @@ Usage: briefing [7|30] [client]
   briefing 7 OHS  — 7-day, OHS only
 """
 
-import json, sys, subprocess, re, readline
+import json, sys, subprocess, re, readline, os
 from datetime import datetime, timezone, timedelta
 
 API_KEY = "b666180ef00fffd23b9a606a4bd8deddea274d2e69fab975583d3d966fbfafed"
@@ -455,6 +455,10 @@ def fetch_and_render(range_days, client):
     if client:
         url += f"&client={client}"
 
+    # Clear screen so briefing always starts at top
+    if sys.stdout.isatty():
+        print("\033[2J\033[H", end="", flush=True)
+
     result = subprocess.run(
         ["curl", "-s", "-H", f"Authorization: Bearer {API_KEY}", url],
         capture_output=True, text=True