MCP tools connected and enabled but never surfaced into the agent's
session toolset on the desktop app + dashboard WebUI (#51587).
There are two independent background MCP discovery thread owners by
surface: tui_gateway.entry (stdio 'hermes --tui') and hermes_cli.mcp_startup
(desktop app + dashboard WS sidecar via tui_gateway/ws.py, and 'hermes
dashboard'). The late-refresh scheduler gates on
tui_gateway.entry.mcp_discovery_in_flight(), which read ONLY the entry
thread global. On the desktop/dashboard surfaces that global is None, so a
server slower than the bounded build-time wait never triggered a late
refresh and its tools stayed invisible for the whole session.
Make mcp_discovery_in_flight() / join_mcp_discovery() consult BOTH thread
owners. Adds the matching in-flight/join helpers to hermes_cli.mcp_startup
and has tui_gateway.entry delegate to them as a second owner.
