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
- System prompt injection for routing
- V1 requirements: C4 docs, ADR, AGENTS.md, debug-log.md
- Design documents in docs/

packages/opencode/test/config/fixtures/markdown-header.md

@@ -0,0 +1,11 @@
+# Response Formatting Requirements
+
+Always structure your responses using clear markdown formatting:
+
+- By default don't put information into tables for questions (but do put information into tables when creating or updating files)
+- Use headings (##, ###) to organise sections, always
+- Use bullet points or numbered lists for multiple items
+- Use code blocks with language tags for any code
+- Use **bold** for key terms and emphasis
+- Use tables when comparing options or listing structured data
+- Break long responses into logical sections with headings