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/.depot/workflows/shellcheck.yml

@@ -0,0 +1,20 @@
+# Depot CI Migration
+# Source: .github/workflows/shellcheck.yml
+#
+# No changes were necessary.
+
+name: Shellcheck
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+jobs:
+  shellcheck:
+    runs-on: depot-ubuntu-24.04
+    steps:
+      - uses: actions/checkout@v6
+      - name: Run shellcheck
+        uses: ludeeus/action-shellcheck@master
+        env:
+          SHELLCHECK_OPTS: "-e SC2148"