M6: Autonomous spec-to-ticket-to-execution pipeline

[islee23520]

Source

• Follow-on roadmap: docs/roadmap-reality-lock.md defines M6 as the autonomous Spec -> Ticket -> agent execution -> T3 Unity verification pipeline.
• Current docs state autonomous spec-to-ticket execution is planned but not yet implemented.

Current state

gateway/src/lux_run_state.rs has M6 states, but the full autonomous pipeline is not implemented or verified.

Acceptance criteria

• A locked spec generates execution-grade tickets automatically.
• Ticket-driven agent execution proceeds through supported gateway/MCP surfaces.
• T3 Unity verification evidence is recorded before a milestone can be pushed.
• Failure paths produce explicit blocker tickets and do not mark the run complete.