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/20260611035744_credential/migration.sql

@@ -0,0 +1,12 @@
+CREATE TABLE `credential` (
+	`id` text PRIMARY KEY,
+	`connector_id` text NOT NULL,
+	`method_id` text NOT NULL,
+	`label` text NOT NULL,
+	`value` text NOT NULL,
+	`active` integer DEFAULT false NOT NULL,
+	`time_created` integer NOT NULL,
+	`time_updated` integer NOT NULL
+);
+--> statement-breakpoint
+CREATE UNIQUE INDEX `credential_connector_active_idx` ON `credential` (`connector_id`) WHERE "credential"."active" = 1;