bug: `WatchEvents` has no context — can't cancel on shutdown

[gitcoder89431]

Problem

WatchEvents in internal/syncthing/client.go has no context.Context parameter, so the long-poll HTTP request (75s timeout) can't be cancelled when the TUI or MCP server shuts down. If the caller is looping, there is also no way to stop it cleanly:

func (c *Client) WatchEvents(since int) ([]SyncEvent, int, error) {
    // no ctx — can't cancel
    if err := c.getLongPoll(path, &raw); err != nil {
        return nil, since, err
    }
    ...
}

Same issue applies to getLongPoll which uses http.NewRequest instead of http.NewRequestWithContext.

Fix

1. Change signature to WatchEvents(ctx context.Context, since int) ([]SyncEvent, int, error)
2. Thread ctx into getLongPoll and use http.NewRequestWithContext
3. Callers (event loop goroutine) should pass a context derived from a root cancel that fires on app quit

This prevents zombie goroutines and ensures clean shutdown.

[gitcoder89431]

Fixed in 0f8ca1d