Add kaizen context resolver for scheduled agent fleet discovery.

Implement discover_kaizen_scheduled_repos and discover_kaizen_projects per
kaizen-agentic ADR-005 contract: State Hub roster, roster.yaml filter, schedule
validation, and prepare_command emission. Register kaizen/resolver/shell source
types with unit tests and runbook dry-run instructions.

pyproject.toml

@@ -12,6 +12,7 @@ dependencies = [
     "alembic>=1.14",
     "nats-py>=2.7",
     "httpx>=0.27",
+    "pyyaml>=6.0",
 ]
 
 [project.optional-dependencies]