Add project scaffold: contracts, schemas, docker-compose, workplans

Phase 0 contracts (event envelope, ActivityDefinition, idempotency doc,
naming conventions) and Phase 1 Temporal cluster setup (docker-compose.dev.yml,
Temporal dynamic config) are complete. Includes Pydantic models, JSON schemas,
wiki architecture docs, and ADR-001 workplan files for both workstreams.

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

scripts/export_schemas.py

@@ -0,0 +1,35 @@
+#!/usr/bin/env python3
+"""
+Export JSON Schemas for the core domain models.
+
+Usage:
+    python scripts/export_schemas.py
+
+Output:
+    schemas/event-envelope.json
+    schemas/activity-definition.json
+
+Run this whenever models.py changes.
+"""
+
+import json
+from pathlib import Path
+
+from activity_core.models import ActivityDefinition, EventEnvelope
+
+SCHEMAS_DIR = Path(__file__).parent.parent / "schemas"
+SCHEMAS_DIR.mkdir(exist_ok=True)
+
+
+def export(model, filename: str) -> None:
+    schema = model.model_json_schema()
+    path = SCHEMAS_DIR / filename
+    path.write_text(json.dumps(schema, indent=2))
+    print(f"  wrote {path.relative_to(Path.cwd())}")
+
+
+if __name__ == "__main__":
+    print("Exporting JSON schemas...")
+    export(EventEnvelope, "event-envelope.json")
+    export(ActivityDefinition, "activity-definition.json")
+    print("Done.")