Initial commit: AirCoding V1.0.0 Alpha architecture baseline

Complete architecture document set with multi-model review remediation:
- Frozen interface contracts, runtime semantics, DB schemas
- Event/tool/error/provider registries
- Scheduler and main agent state machines
- C4 module/code views, solution architecture, baseline V1
- Multi-model review reports and joint assessment
- Phase-gate remediation complete (P0/P1/P2/UX resolved)
- Implementation plan with T-000A through T-045
- Reference folders kept as placeholders only

reference/atuin-18.16.1/.github/workflows/nix.yml

@@ -0,0 +1,34 @@
+# Verify the Nix build is working
+# Failures will usually occur due to an out of date Rust version
+# That can be updated to the latest version in nixpkgs-unstable with `nix flake update`
+name: Nix
+on:
+  push:
+    branches: [ main ]
+    paths-ignore:
+      - 'ui/**'
+  pull_request:
+    branches: [ main ]
+    paths-ignore:
+      - 'ui/**'
+
+jobs:
+  check:
+    runs-on: depot-ubuntu-24.04
+
+    steps:
+      - uses: actions/checkout@v6
+      - uses: cachix/install-nix-action@v31
+
+      - name: Run nix flake check
+        run: nix flake check --print-build-logs
+
+  build-test:
+    runs-on: depot-ubuntu-24.04
+
+    steps:
+      - uses: actions/checkout@v6
+      - uses: cachix/install-nix-action@v31
+
+      - name: Run nix build
+        run: nix build --print-build-logs