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-change-size/SKILL.md

@@ -0,0 +1,11 @@
+---
+name: code-review-change-size
+description: Change size guidance (800 lines)
+---
+
+Unless the change is mechanical the total number of changed lines should not exceed 800 lines.
+For complex logic changes the size should be under 500 lines.
+
+If the change is larger, explain whether it can be split into reviewable stages and identify the smallest coherent stage to land first.
+Base the staging suggestion on the actual diff, dependencies, and affected call sites.
+