Wire OrchestratorAgent against the full compose order end-to-end

[linus10x]

OrchestratorAgent.process() returns None in v0.2. The full compose order per ARCHITECTURE.md is documented but unwired:

DEFCON → Domain pre-flight → Sovereign Veto → Autonomy Ladder gate → Shadow Mode → Audit write → ACTION

Scope:

1. Implement the full pipeline in OrchestratorAgent.process
2. Add one orchestrator-driven end-to-end example to examples/
3. Add integration tests covering the compose-order short-circuit behaviors (DEFCON denies → skip everything; Sovereign Veto vetoes → audit-write + halt)
4. Add a sequence diagram to ARCHITECTURE.md showing the compose order

Priority: P1. Composite 16/27.