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/openai-codex/.codex/skills/code-review-testing/SKILL.md

@@ -0,0 +1,14 @@
+---
+name: code-review-testing
+description: Test authoring guidance
+---
+
+For agent changes prefer integration tests over unit tests. Integration tests are under `core/suite` and use `test_codex` to set up a test instance of codex.
+
+Features that change the agent logic MUST add an integration test:
+- Provide a list of major logic changes and user-facing behaviors that need to be tested.
+
+If unit tests are needed, put them in a dedicated test file (*_tests.rs).
+Avoid test-only functions in the main implementation.
+
+Check whether there are existing helpers to make tests more streamlined and readable.