The port-announcement clock in waitForDashboardPort starts the instant the
backend process is spawned — before uvicorn binds its socket. On a cold
install the child first compiles and imports the whole hermes_cli.main ->
web_server -> FastAPI/uvicorn chain, and on Windows real-time AV scans every
freshly written .pyc. That pre-bind cost can exceed the old hardcoded 45s
deadline, so the desktop killed a healthy-but-still-starting backend and
respawned it, piling up orphaned processes (#50209).
Raise the default to 90s and make it overridable via
HERMES_DESKTOP_PORT_ANNOUNCE_TIMEOUT_MS, clamped to a 45s floor so a bad
override can't reintroduce the loop. Warm starts still announce in well under
a second; both call sites inherit the new default with no change. Adds
backend-ready.test.cjs (wired into test:desktop:platforms).
