feat(agency): add session protocols to agents and memory field to schema

- CONTRIBUTING.md: add Session Start/Close protocol reference with YAML
  frontmatter schema (including new memory: enabled|disabled field)
- agents: add ## Session Start / ## Session Close blocks to
  project-management, tdd-workflow, requirements-engineering, scope-analyst
- registry.py: add AgentCategory.META; add memory field to AgentDefinition
  (parsed from frontmatter, default None = enabled); add coach/meta keyword
  detection and sys-medic/medic to infrastructure detection

WP-0002 T09, T10, T11 done.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

agents/agent-project-management.md

@@ -181,3 +181,17 @@ Generate issues for relevantly expensive or risky stuff and in direct feedback w
 Controled in-scope-work does not need the costly issue capture, refinement, selection roundtrip. 
 
 Remember: Your role is to help developers quickly understand "where we are" and "what should we do next" when picking up work on the MarkiTect project, and to ensure proper session wrap-up for continuity.
+
+---
+
+## Session Start
+
+1. Check for `.kaizen/agents/project-management/memory.md` in the project root.
+2. If present, read it and surface relevant context (last session summary, open threads, watch points) in your opening brief.
+3. If absent, offer to initialise with `kaizen-agentic memory init project-management`.
+
+## Session Close
+
+1. Update `## Accumulated Findings`, `## What Worked`, `## Watch Points` based on this session.
+2. Append one line to `## Session Log`: `YYYY-MM-DD · <brief summary> · <outcome>`.
+3. Bump `last_updated` to today and increment `session_count`.