feat(scanner): Complete PoE implementation with Windows compatibility fix

- Fix namespace conflicts (Subgraph → PoESubgraph)
- Add hash sanitization for Windows filesystem (colon → underscore)
- Update all test mocks to use It.IsAny<>()
- Add direct orchestrator unit tests
- All 8 PoE tests now passing (100% success rate)
- Complete SPRINT_3500_0001_0001 documentation

Fixes compilation errors and Windows filesystem compatibility issues.
Tests: 8/8 passing
Files: 8 modified, 1 new test, 1 completion report

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

docs2/developer/onboarding.md

@@ -0,0 +1,15 @@
+# Developer onboarding (summary)
+
+## Prerequisites
+- .NET 10 SDK
+- Node and npm for UI development
+- Docker for local infrastructure
+
+## Local stack
+- PostgreSQL, Valkey, and RustFS are required.
+- Services use layered configuration (env, appsettings, YAML).
+
+## Common workflows
+- Run the stack with compose or Helm profiles.
+- Debug a single service by running it locally and pointing others to localhost.
+- Use deterministic fixtures for replay and policy validation.