feat(aircoding): AirCoding V2 baseline — deterministic multi-agent architecture

Forked from OpenCode v1.17.4 with multi-agent system:
- 5 agents: aircoding, scheduler, worker, architect, reviewer
- Deterministic DAG scheduling engine (coordinator_tick)
- Tool whitelists as hard enforcement
- AirCoding validation plugin
- V1 requirements: C4 docs, ADR, AGENTS.md, debug-log.md
- Design documents in docs/

packages/desktop/src/main/constants.ts

@@ -0,0 +1,7 @@
+import { app } from "electron"
+
+type Channel = "dev" | "beta" | "prod"
+const raw = import.meta.env.OPENCODE_CHANNEL
+export const CHANNEL: Channel = raw === "dev" || raw === "beta" || raw === "prod" ? raw : "dev"
+
+export const UPDATER_ENABLED = app.isPackaged && CHANNEL !== "dev"