feat(cli): watch files with event streams

- Add a private SSE endpoint that emits file change events for authenticated clients.
- Replace the watch sleep loop with watchdog local file events and remote SSE triggers.
- Debounce local event bursts and keep watch running after transient sync failures.
- Add watchdog as a standalone CLI dependency and cover watch behavior in tests.
- Bump NanoShare to 1.25.0 and the standalone CLI to 0.4.0.

cli/nanoshare_client/cli.py

@@ -3,7 +3,6 @@ from __future__ import annotations
 import argparse
 import json
 import sys
-import time
 from pathlib import Path
 
 from .app import make_client
@@ -14,6 +13,7 @@ from .config import DEFAULT_CONFIG
 from .remote_path import join_remote_path
 from .sync import sync_once
 from .table import format_table
+from .watch import watch_loop
 
 DEFAULT_NODE = 'picoshare'
 
@@ -99,12 +99,7 @@ def _cmd_sync(args) -> int:
     client.close()
 
 def _cmd_watch(args) -> int:
-  print(f'watching {args.folder} every {args.interval}s')
-  while True:
-    code = _cmd_sync(args)
-    if code:
-      return code
-    time.sleep(args.interval)
+  return watch_loop(args, _cmd_sync)
 
 def _cmd_completion(args) -> int:
   try: