Implement prototype: venue-driven simulation core, scenarios, tests, and playable entrance scene

- Godot 4.3 project scaffold with first-person guard, procedural world,
  interaction HUD, access inspection, radio forms, debug overlay, shift review
- Simulation core: ShiftCoordinator, VenueScenario, EventScheduler, NPCController/FSM,
  AccessVerifier, EscalationManager, RadioSystem, IncidentRecorder,
  ReputationEvaluator, CrowdSystem, EventBus
- Three authored scenarios (Hollywood Blvd building, The Joke Shop, TV studio)
- Custom headless test runner (25 tests) replacing editor-dependent GUT,
  plus GitHub Actions CI
- Documentation workflow live: README, PLAN (tech stack), TODO/DONE, MEMORY

.github/workflows/ci.yml

@@ -0,0 +1,44 @@
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+
+jobs:
+  headless-tests:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install Godot 4.3
+        run: |
+          curl -sL -o /tmp/godot.zip \
+            https://github.com/godotengine/godot/releases/download/4.3-stable/Godot_v4.3-stable_linux.x86_64.zip
+          unzip -o /tmp/godot.zip -d /tmp/godot-bin
+          sudo install /tmp/godot-bin/Godot_v4.3-stable_linux.x86_64 /usr/local/bin/godot
+
+      - name: Cache .godot import artifacts
+        uses: actions/cache@v4
+        with:
+          path: .godot
+          key: godot-import-${{ hashFiles('project.godot', 'src/**/*.gd') }}
+
+      - name: Import project (build class cache)
+        run: godot --headless --import || true
+
+      - name: Run headless test suite
+        run: |
+          set +e
+          output=$(godot --headless --path . --script res://src/test/test_runner.gd 2>&1)
+          status=$?
+          echo "$output"
+          if [ $status -ne 0 ]; then
+            echo "::error::Headless tests failed"
+            exit 1
+          fi
+          if echo "$output" | grep -q "SCRIPT ERROR"; then
+            echo "::error::Script errors detected"
+            exit 1
+          fi
+          exit 0