fix(gate-b): fresh-db install path - conditional guards on plugin-table migrations + dual-path convergence migrations

app/plugins/builtins/tasks/migrations/0002_unified_task_system.sql

@@ -0,0 +1,31 @@
+-- Dual-path convergence (Gate B): apply the unified task system that
+-- Alembic migrations 0124 (columns/indexes/FK) and 0127 (drop legacy FK)
+-- create on the core path. Idempotent so both install paths converge to
+-- the identical schema. The end state has NO foreign key on contact_id.
+ALTER TABLE tasks ADD COLUMN IF NOT EXISTS assignee_type VARCHAR(20) NOT NULL DEFAULT 'user';
+ALTER TABLE tasks ADD COLUMN IF NOT EXISTS assignee_id UUID;
+ALTER TABLE tasks ADD COLUMN IF NOT EXISTS entity_type VARCHAR(80);
+ALTER TABLE tasks ADD COLUMN IF NOT EXISTS entity_id UUID;
+ALTER TABLE tasks ADD COLUMN IF NOT EXISTS creator_type VARCHAR(20) NOT NULL DEFAULT 'user';
+ALTER TABLE tasks ADD COLUMN IF NOT EXISTS creator_id UUID;
+ALTER TABLE tasks ADD COLUMN IF NOT EXISTS parent_task_id UUID;
+ALTER TABLE tasks ADD COLUMN IF NOT EXISTS depends_on JSONB NOT NULL DEFAULT '[]'::jsonb;
+ALTER TABLE tasks ADD COLUMN IF NOT EXISTS task_type VARCHAR(30) NOT NULL DEFAULT 'todo';
+ALTER TABLE tasks ADD COLUMN IF NOT EXISTS success_criteria JSONB;
+ALTER TABLE tasks ADD COLUMN IF NOT EXISTS target_date TIMESTAMPTZ;
+ALTER TABLE tasks ADD COLUMN IF NOT EXISTS progress INTEGER NOT NULL DEFAULT 0;
+
+CREATE INDEX IF NOT EXISTS ix_tasks_tenant_entity ON tasks(tenant_id, entity_type, entity_id);
+CREATE INDEX IF NOT EXISTS ix_tasks_tenant_assignee ON tasks(tenant_id, assignee_type, assignee_id);
+CREATE INDEX IF NOT EXISTS ix_tasks_tenant_parent ON tasks(tenant_id, parent_task_id);
+CREATE INDEX IF NOT EXISTS ix_tasks_tenant_type ON tasks(tenant_id, task_type);
+
+DO $$
+BEGIN
+    IF NOT EXISTS (
+        SELECT 1 FROM pg_constraint WHERE conname = 'fk_tasks_parent_task_id'
+    ) THEN
+        ALTER TABLE tasks ADD CONSTRAINT fk_tasks_parent_task_id
+            FOREIGN KEY (parent_task_id) REFERENCES tasks(id) ON DELETE CASCADE;
+    END IF;
+END $$;