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/core/migration/20260323234822_events/migration.sql

@@ -0,0 +1,13 @@
+CREATE TABLE `event_sequence` (
+	`aggregate_id` text PRIMARY KEY,
+	`seq` integer NOT NULL
+);
+--> statement-breakpoint
+CREATE TABLE `event` (
+	`id` text PRIMARY KEY,
+	`aggregate_id` text NOT NULL,
+	`seq` integer NOT NULL,
+	`type` text NOT NULL,
+	`data` text NOT NULL,
+	CONSTRAINT `fk_event_aggregate_id_event_sequence_aggregate_id_fk` FOREIGN KEY (`aggregate_id`) REFERENCES `event_sequence`(`aggregate_id`) ON DELETE CASCADE
+);