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/core/migration/20260510033149_session_usage/migration.sql

@@ -0,0 +1,6 @@
+ALTER TABLE `session` ADD `cost` real DEFAULT 0 NOT NULL;--> statement-breakpoint
+ALTER TABLE `session` ADD `tokens_input` integer DEFAULT 0 NOT NULL;--> statement-breakpoint
+ALTER TABLE `session` ADD `tokens_output` integer DEFAULT 0 NOT NULL;--> statement-breakpoint
+ALTER TABLE `session` ADD `tokens_reasoning` integer DEFAULT 0 NOT NULL;--> statement-breakpoint
+ALTER TABLE `session` ADD `tokens_cache_read` integer DEFAULT 0 NOT NULL;--> statement-breakpoint
+ALTER TABLE `session` ADD `tokens_cache_write` integer DEFAULT 0 NOT NULL;