Move workflow-cleanup subscriber + tool-timeout boot seed out of start_channels

[oxoxDev]

Summary

Two always-on registrations run only inside start_channels (channels/runtime/startup.rs): skills::bus::register_workflow_cleanup_subscriber and the boot-time set_tool_timeout_secs seed. spawn_channels_service skips start_channels when no channel is configured, so web-chat-only / channel-less cores never get them today — a pre-existing gap, unchanged by the channels gate (#4801) but made more visible by it (a channels-off build also skips them).

Same class as #5003 (learning) and #5002 (web_chat): non-channel infra wired into the channels bootstrap by accident of history.

Ask

Move both to the always-on bootstrap path (core::jsonrpc::register_domain_subscribers / start_bootstrap_jobs) so they run regardless of channel configuration.

Related

• feat(core): feature gate — channels & webviews #4801, fix(learning): email-signature subscriber + rebuild trigger silently depend on channels being configured #5003, refactor(core): relocate the web chat conduit out of channels/ #5002
• Epic Feature gates for core subsystems — tracking (lightweight harness builds) #4795