* Gate `browser.progress` emit on truthy `session_id`. The TUI
prints `messages` from the response when there's no session, so
emitting events too would double-render. Now: with a session →
events stream live; without one → bundled messages only.
* Resolve `system = platform.system()` once in `_browser_connect`
and thread it through `try_launch_chrome_debug` and
`_failure_messages` → `manual_chrome_debug_command`, so the
generated hint is consistent (and tests are deterministic) on
any host.
* Add `test_browser_manage_connect_no_session_skips_progress_events`
to lock in the gating behavior.
679a27498d