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

AirPlan/docs/architecture/adr/ADR-0003-use-project-local-air-state.md

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+# ADR-0003: Use Project-Local `.air` State
+
+- Status: Accepted
+- Date: 2026-05-27
+
+## Context
+
+AirCoding sessions, artifacts, rules, plans, backups, and debug evidence must be resumable and portable with the project where possible, while still keeping private/local state out of normal source sharing.
+
+## Decision
+
+Use project-local `.air/` as the source of truth:
+
+```text
+<project>/.air/shared/  # git-shareable project config, rules, plan docs
+<project>/.air/local/   # private sessions, artifacts, backups, workspaces, local DBs
+```
+
+Session DBs live at:
+
+```text
+<project>/.air/local/sessions/<session-id>/session.db
+```
+
+## Consequences
+
+- Project state can move with the project directory.
+- `.air/shared/` can be versioned; `.air/local/` is gitignored by default.
+- Runtime recovery uses project-local SQLite and artifacts.
+- Global `~/.air/` remains config/cache/log/index state, not session source of truth.