Add Matrix helper CLI

[mdheller]

Summary

Adds agent-term-matrix, a focused helper command for Matrix send and sync-normalization workflows backed by the Matrix service seam.

This PR adds:

• matrix_cli.py with send and normalize-sync subcommands.
• agent-term-matrix console script.
• send workflow routed through the AgentTerm dispatch pipeline so Matrix sends remain policy-gated and E2EE-gated.
• normalize-sync workflow for Matrix /sync JSON payloads with optional EventStore persistence.
• Tests for policy-admitted Matrix send, E2EE-blocked sensitive send, sync normalization output, and sync persistence.

Boundary decisions

• agent-term-matrix send uses the dispatch pipeline, not a direct unmanaged Matrix send.
• Matrix sends still require Policy Fabric admission.
• Sensitive sends still fail closed when Matrix E2EE posture is unacceptable.
• normalize-sync does not require live homeserver credentials and remains CI-safe.
• Live sync token/state handling remains a follow-up lane.

Validation

Expected CI:

ruff check .
pytest

Next lane after merge: live Matrix sync-token/state handling and room alias resolution.