fix(whatsapp): hide bridge console window on Windows

[vqardy]

Summary

On Windows the WhatsApp bridge (node.exe ... whatsapp-bridge/bridge.js) is spawned with start_new_session=True, which is a no-op on Windows — subprocess accepts the kwarg but ignores it, so the long-lived bridge pops a visible black console window. Closing it kills the bridge, and the gateway's reconnection watcher relaunches it, so it never stays closed.

Other subprocess calls in the same file (_kill_stale_bridge_by_pidfile, _kill_port_process) already use windows_hide_flags() (CREATE_NO_WINDOW); the bridge spawn simply omitted it.

Change

Add creationflags=windows_hide_flags() to the bridge Popen. windows_hide_flags() returns 0 on POSIX, so this is a no-op there. Bridge output still routes to the log file, so stdio capture is unaffected.

Verification

• Live bridge now reports MainWindowHandle=0 (no window) and the gateway logs ✓ whatsapp connected.
• tests/gateway/test_whatsapp_connect.py (29 tests), test_whatsapp_stale_bridge.py, test_whatsapp_reply_prefix.py pass.
• test_whatsapp_bridge_pidfile.py::TestKillPortProcess::test_kill_port_spares_client_process is pre-existing flaky on Windows (real socket + taskkill timing) — fails identically on unmodified code.

🤖 Generated with Hermes Agent

[alt-glitch]

This was generated by AI during triage.

Competing fix cluster for the WhatsApp bridge console window on Windows (issue #60508 / closed #29715). Three OPEN PRs:

• fix(whatsapp): hide bridge console window on Windows #60605 (this) and fix(gateway/whatsapp): hide node.exe console on Windows via CREATE_NO_WINDOW (#29715) #29807 add creationflags=windows_hide_flags() (hide-only via CREATE_NO_WINDOW).
• fix(whatsapp): hide bridge console window on Windows #59285 uses windows_detach_popen_kwargs() which additionally DETACHES the bridge (breakaway/detached-process), so closing the console no longer kills+respawns it.

All fix the same symptom; #59285 is the more complete fix (hide + detach addresses the crash-loop, not just the visible window). Flagging for a maintainer to pick one.

[teknium1]

Thanks for this PR — the underlying bug (WhatsApp bridge spawning Node with a visible console window on Windows) is now fixed on main via #60924, a salvage of #60647 which swaps the bare start_new_session=True for the shared windows_detach_popen_kwargs() helper. Several PRs targeted this same symptom; we merged the minimal variant that reuses the sanctioned helper. Your report/fix helped confirm the bug class — appreciated. Closing as superseded.