Add governed repo-local learning and playbook update flow for agents

[mdheller]

Context

The SourceOS Agent Reliability Standard requires that durable agent learnings become governed memory, not untraceable chat residue.

MemoryMesh should own repo/project/user/org memory provenance and playbook reconciliation for agent reliability.

Scope

Implement governed memory update flow for agent sessions:

• agent identifies a durable operational learning
• agent proposes a memory/playbook update as a diff or artifact
• destination scope is explicit: repo, project, user, org, enterprise
• conflicting playbook entries are reconciled, not duplicated
• high-impact memory updates require human review
• accepted updates record source session, reason, approver, and affected repo/policy/runtime surface

Repo-local targets

Support standardized repo-local paths:

SOURCEOS.md
AGENTS.md
.sourceos/memory/
.sourceos/workflows/
.sourceos/policies/
.sourceos/handoff/

Acceptance criteria

• AgentPlane/guardrail-fabric sessions can emit proposed memory update artifacts.
• MemoryMesh can ingest and classify proposed learnings by scope.
• Playbook updates are reviewable and provenance-linked.
• A repo can distinguish accepted durable knowledge from transient session notes.

Non-goals

• Do not allow silent mutation of governance memory.
• Do not require cloud sync for local memory capture.