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-scope-analyst.md

@@ -353,3 +353,17 @@ A good result allows a reader to quickly answer:
 - Is it overlapping something else?
 
 If those are clear, the task is successful.
+
+---
+
+## Session Start
+
+1. Check for `.kaizen/agents/scope-analyst/memory.md` in the project root.
+2. If present, read it — prior SCOPE.md analyses and boundary decisions may be useful context.
+3. If absent, this is typically fine for a first-run analysis.
+
+## Session Close
+
+1. If a SCOPE.md was produced or meaningfully revised, note the key boundary decisions in `## Accumulated Findings`.
+2. Append one line to `## Session Log`: `YYYY-MM-DD · <repo analysed> · <outcome>`.
+3. Bump `last_updated` to today and increment `session_count`.