feat: scaffold BlackRoad OS Phase 2 infrastructure

Implements complete Phase 2 scaffold across 6 core modules:

## New Modules

### 1. Backend API Enhancements
- Add system router with /version, /config/public, /os/state endpoints
- Register system router in main.py
- Add comprehensive tests for system endpoints

### 2. Core OS Runtime (core_os/)
- Implement UserSession, Window, OSState models
- Add state management functions (open_window, close_window, etc.)
- Create Backend API adapter for communication
- Include full test suite for models and state

### 3. Operator Engine (operator_engine/)
- Build job registry with example jobs
- Implement simple scheduler with lifecycle management
- Optional HTTP server on port 8001
- Complete tests for jobs and scheduler

### 4. Web Client Enhancements
- Add CoreOSClient JavaScript class
- Integrate system API endpoints
- Event-driven architecture for state updates
- Zero dependencies, vanilla JavaScript

### 5. Prism Console (prism-console/)
- Modern dark-themed admin UI
- Multi-tab navigation (Overview, Jobs, Agents, Logs, System)
- Real-time metrics dashboard
- Backend API integration with auto-refresh

### 6. Documentation (codex-docs/)
- Complete MkDocs-based documentation
- Architecture guides and component docs
- Infrastructure setup guides
- API reference documentation

## CI/CD

- Add core-os-tests.yml workflow
- Add operator-tests.yml workflow
- Add docs-build.yml workflow

## Documentation

- Create BLACKROAD_OS_REPO_MAP.md cross-reference
- Add README for each module
- Comprehensive integration documentation

## Summary

- 37 new files created
- ~3,500 lines of new code
- 5 test suites with 15+ tests
- 3 new CI workflows
- 10+ documentation pages

All modules are minimal working skeletons ready for integration.
Designed to be extracted into separate repos if needed.

Phase 2 scaffold complete and ready for review.

backend/tests/test_system.py

@@ -0,0 +1,60 @@
+"""Tests for system endpoints"""
+import pytest
+from httpx import AsyncClient
+
+
+@pytest.mark.asyncio
+async def test_version_endpoint(client: AsyncClient):
+    """Test /api/system/version endpoint"""
+    response = await client.get("/api/system/version")
+    assert response.status_code == 200
+
+    data = response.json()
+    assert "version" in data
+    assert "build_time" in data
+    assert "env" in data
+    assert "git_sha" in data
+    assert "app_name" in data
+    assert data["app_name"] == "BlackRoad Operating System"
+
+
+@pytest.mark.asyncio
+async def test_public_config_endpoint(client: AsyncClient):
+    """Test /api/system/config/public endpoint"""
+    response = await client.get("/api/system/config/public")
+    assert response.status_code == 200
+
+    data = response.json()
+    assert "environment" in data
+    assert "app_name" in data
+    assert "version" in data
+    assert "features" in data
+    assert "limits" in data
+    assert "external_services" in data
+
+    # Verify features structure
+    features = data["features"]
+    assert "blockchain_enabled" in features
+    assert "ai_agents_enabled" in features
+    assert "video_streaming_enabled" in features
+
+    # Verify limits structure
+    limits = data["limits"]
+    assert "max_upload_size_mb" in limits
+    assert "session_timeout_minutes" in limits
+
+
+@pytest.mark.asyncio
+async def test_os_state_endpoint(client: AsyncClient):
+    """Test /api/system/os/state endpoint (stub)"""
+    response = await client.get("/api/system/os/state")
+    assert response.status_code == 200
+
+    data = response.json()
+    assert "status" in data
+    assert data["status"] == "ok"
+    assert "active_windows" in data
+    assert "running_apps" in data
+    assert "system_resources" in data
+    assert isinstance(data["active_windows"], list)
+    assert isinstance(data["running_apps"], list)