chore: my-deepagent-seed (BudgetTracker PoC + v0.1.0 seed assets)

Pre-flight assets prepared on the main machine before the new-machine
rewrite of my-deepagent in Python.

- poc/: BudgetTracker + CostMiddleware + MockChatModel PoC.
  Validates wrap_model_call pattern, SQLite WAL + ON CONFLICT upsert,
  per-scope cap accounting. 5/5 pytest PASS in isolated uv venv.
- schemas/: 10 personas (Anthropic Sonnet/Opus/Haiku + DeepSeek mix),
  3 workflows (spec-and-review, bug-fix-with-reproduction,
  code-investigation), 4 artifact JSON Schemas (dev/spec@1,
  dev/phase-plan@1, dev/review-finding-batch@1, common/final-report@1).
- schemas/validate.py: pydantic + Draft202012 cross-validation.
  18/18 assets verified.
- README.md: new-machine bootstrap instructions.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

my-deepagent-seed/poc/main.py

@@ -0,0 +1,6 @@
+def main():
+    print("Hello from poc!")
+
+
+if __name__ == "__main__":
+    main()