Sync with main after the contribution-shell refactor (#60638) and the backendConnectionState extraction (#65885) landed. Seven conflicts, all resolved in favor of main's new architecture with the SSH lifecycle ported on top:
- electron/main.ts: adopt backendConnectionState (attempt tokens, attachProcess, clearPromiseForAttempt) as the sole owner of the primary backend; drop the branch's raw hermesProcess/connectionPromise globals and commitConnectionFailure call site. SSH liveness-streak classification, teardown, and the SSH quit path are layered onto the new ownership model; before-quit combines SSH transactional teardown with the Windows sandbox marker (#38216).
- desktop-controller.tsx: deleted on main; its SSH beforeConnectionSwitch cleanup (preserved-route fresh draft, overlay return-route reset, project-tree reset, close-all-terminals) moves to contrib/wiring.tsx's useGatewayBoot call.
- use-session-actions/index.ts: keep main's onFreshDraftRouteIntent (fires unconditionally); preserveRoute gates only the navigate.
- gateway-settings.tsx: keep main's acceptSavedConfig/connectedCloudUrl; every save/sign-in/sign-out success path routes through acceptSavedConfig with the branch's stale-async seq guards intact.
- boot-failure-reauth.ts: keep both sshFailureMessage and main's isRemoteReauthFailure formatting.
- Both test harnesses take the union of props.
Validation: tsc -b clean; desktop suite 1704 passed / 1 skipped; electron SSH/connection modules 225 passed; python SSH + web_server suites 508 passed.
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