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>

src/kaizen_agentic/registry.py

@@ -17,6 +17,7 @@ class AgentCategory(Enum):
     INFRASTRUCTURE = "infrastructure"
     TESTING = "testing"
     DOCUMENTATION = "documentation"
+    META = "meta"
 
 
 @dataclass
@@ -29,6 +30,7 @@ class AgentDefinition:
     category: AgentCategory
     dependencies: Set[str]
     model: Optional[str] = None
+    memory: Optional[str] = None  # "enabled" (default) | "disabled"
 
     @classmethod
     def from_file(cls, file_path: Path) -> "AgentDefinition":
@@ -56,6 +58,7 @@ class AgentDefinition:
             category=category,
             dependencies=dependencies,
             model=frontmatter.get("model"),
+            memory=frontmatter.get("memory"),
         )
 
     @staticmethod
@@ -127,8 +130,12 @@ class AgentDefinition:
         if any(keyword in name_lower for keyword in ["documentation", "claude"]):
             return AgentCategory.DOCUMENTATION
 
+        # Meta agents (coaching, cross-agent orchestration)
+        if any(keyword in name_lower for keyword in ["coach", "meta"]):
+            return AgentCategory.META
+
         # Infrastructure agents
-        if any(keyword in name_lower for keyword in ["setup", "repository", "tooling"]):
+        if any(keyword in name_lower for keyword in ["setup", "repository", "tooling", "sys-medic", "medic"]):
             return AgentCategory.INFRASTRUCTURE
 
         # Development process agents