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/opencode/src/cli/cmd/debug/skill.ts

@@ -0,0 +1,15 @@
+import { EOL } from "os"
+import { Effect } from "effect"
+import { Skill } from "../../../skill"
+import { effectCmd } from "../../effect-cmd"
+
+export const SkillCommand = effectCmd({
+  command: "skill",
+  describe: "list all available skills",
+  builder: (yargs) => yargs,
+  handler: Effect.fn("Cli.debug.skill")(function* () {
+    const skill = yield* Skill.Service
+    const skills = yield* skill.all()
+    process.stdout.write(JSON.stringify(skills, null, 2) + EOL)
+  }),
+})