Add operator dispatch pipeline

[mdheller]

Summary

Adds the first tested operator dispatch pipeline for AgentTerm.

This PR wires the existing scaffolds together without creating a new authority plane. The pipeline records every input, gate, decision, adapter result, and TUI snapshot source event in the local event log.

It adds:

• pipeline.py with OperatorDispatchPipeline, DispatchPipelineConfig, and DispatchOutcome.
• Matrix E2EE posture gate before sensitive context release.
• Agent Registry identity/tool-grant gates for non-human participants.
• Policy Fabric admission gate for side-effecting and sensitive events.
• Adapter selection and fail-closed no-adapter handling.
• EventStore persistence for the original event plus all gate/result events.
• TUI snapshot generation after dispatch.
• Tests for successful dispatch, unknown participant blocking, registered participant flow, policy denial, Matrix E2EE blocking, no-adapter fail-closed behavior, and full sensitive-context allowed flow.

Boundary decisions

• The pipeline is orchestration only. It does not own Matrix, Agent Registry, Policy Fabric, AgentPlane, cloudshell-fog, or any SourceOS plane authority.
• Every gate/result is recorded as an event; no hidden decisions.
• Matrix posture blocks before policy/adapters when sensitive context is unsafe.
• Agent Registry blocks before policy/adapters for unresolved participants.
• Policy Fabric blocks before adapter dispatch for side-effecting or sensitive events.
• Missing adapter is a fail-closed event, not a silent no-op.

Validation

Expected CI:

ruff check .
pytest

Next lane after merge: add a thin operator CLI command for dispatching through the pipeline with configured in-memory/default adapters, then evolve toward live service-backed adapters.