Delete code paths that never executed in the serve/API/remote stack:
- BridgeCancelledError: raised but never caught; replace raises with RuntimeError and drop the class.
- InputBridge.error setter and _error field: written at the handler layer, never read (session.auth_error is the surfaced channel).
- cancel_event param and _check_cancel inner fn on _perform_download: the only caller always passed None (the live job.cancel_event is untouched).
- result_with_progress monkeypatch: its status pings were redundant with the file-polled progress_sink, which is now the sole path.
- session param on _resolve_manifest_data: unused in the body.
Reconcile SessionStore's hardcoded 600s auth-state TTL into a shared AUTH_INPUT_TIMEOUT constant referenced by both the InputBridge input timeout and the store, removing the magic number without changing the longer grace window.
Update input_bridge/session_store tests for the new channels and add an assertion that auth-state entries expire at the single rule.
Covers RemoteClient/RemoteService, REST routes, handlers, SessionStore, InputBridge, DownloadQueueManager, errors, compression, and serve CLI. E2e tier opts in via --live and can auto-spawn its own serve.
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