feat: add database migrations for DAG and worker system

Migration 014: dag_nodes, dag_edges, dag_cross_edges tables for the
feature-level dependency graph with validation state tracking.

Migration 015: runners, job_definitions, jobs, job_log tables for the
async compute job system with PostgreSQL-backed work queue.

Update TruncateAll in testutil to include new tables.

migrations/015_jobs_runners.sql

@@ -0,0 +1,109 @@
+-- Worker system: runners, job definitions, jobs, and job log.
+-- Migration: 015_jobs_runners
+-- Date: 2026-02
+
+BEGIN;
+
+--------------------------------------------------------------------------------
+-- Runners (registered compute workers)
+--------------------------------------------------------------------------------
+
+CREATE TABLE runners (
+    id              UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    name            TEXT UNIQUE NOT NULL,
+    token_hash      TEXT NOT NULL,
+    token_prefix    TEXT NOT NULL,
+    tags            TEXT[] NOT NULL DEFAULT '{}',
+    status          TEXT NOT NULL DEFAULT 'offline',
+    last_heartbeat  TIMESTAMPTZ,
+    last_job_id     UUID,
+    metadata        JSONB DEFAULT '{}',
+    created_at      TIMESTAMPTZ NOT NULL DEFAULT now(),
+    updated_at      TIMESTAMPTZ NOT NULL DEFAULT now()
+);
+
+CREATE INDEX idx_runners_status ON runners(status);
+CREATE INDEX idx_runners_token ON runners(token_hash);
+
+--------------------------------------------------------------------------------
+-- Job Definitions (parsed from YAML, stored for reference and FK)
+--------------------------------------------------------------------------------
+
+CREATE TABLE job_definitions (
+    id              UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    name            TEXT UNIQUE NOT NULL,
+    version         INTEGER NOT NULL DEFAULT 1,
+    trigger_type    TEXT NOT NULL,
+    scope_type      TEXT NOT NULL,
+    compute_type    TEXT NOT NULL,
+    runner_tags     TEXT[] NOT NULL DEFAULT '{}',
+    timeout_seconds INTEGER NOT NULL DEFAULT 600,
+    max_retries     INTEGER NOT NULL DEFAULT 1,
+    priority        INTEGER NOT NULL DEFAULT 100,
+    definition      JSONB NOT NULL,
+    enabled         BOOLEAN NOT NULL DEFAULT true,
+    created_at      TIMESTAMPTZ NOT NULL DEFAULT now(),
+    updated_at      TIMESTAMPTZ NOT NULL DEFAULT now()
+);
+
+CREATE INDEX idx_job_defs_trigger ON job_definitions(trigger_type);
+CREATE INDEX idx_job_defs_enabled ON job_definitions(enabled) WHERE enabled = true;
+
+--------------------------------------------------------------------------------
+-- Jobs (individual compute job instances)
+--------------------------------------------------------------------------------
+
+CREATE TYPE job_status AS ENUM (
+    'pending', 'claimed', 'running', 'completed', 'failed', 'cancelled'
+);
+
+CREATE TABLE jobs (
+    id                UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    job_definition_id UUID REFERENCES job_definitions(id) ON DELETE SET NULL,
+    definition_name   TEXT NOT NULL,
+    status            job_status NOT NULL DEFAULT 'pending',
+    priority          INTEGER NOT NULL DEFAULT 100,
+    item_id           UUID REFERENCES items(id) ON DELETE CASCADE,
+    project_id        UUID REFERENCES projects(id) ON DELETE SET NULL,
+    scope_metadata    JSONB DEFAULT '{}',
+    runner_id         UUID REFERENCES runners(id) ON DELETE SET NULL,
+    runner_tags       TEXT[] NOT NULL DEFAULT '{}',
+    created_at        TIMESTAMPTZ NOT NULL DEFAULT now(),
+    claimed_at        TIMESTAMPTZ,
+    started_at        TIMESTAMPTZ,
+    completed_at      TIMESTAMPTZ,
+    timeout_seconds   INTEGER NOT NULL DEFAULT 600,
+    expires_at        TIMESTAMPTZ,
+    progress          INTEGER DEFAULT 0,
+    progress_message  TEXT,
+    result            JSONB,
+    error_message     TEXT,
+    retry_count       INTEGER NOT NULL DEFAULT 0,
+    max_retries       INTEGER NOT NULL DEFAULT 1,
+    created_by        TEXT,
+    cancelled_by      TEXT
+);
+
+CREATE INDEX idx_jobs_status ON jobs(status);
+CREATE INDEX idx_jobs_pending ON jobs(status, priority, created_at)
+    WHERE status = 'pending';
+CREATE INDEX idx_jobs_item ON jobs(item_id);
+CREATE INDEX idx_jobs_runner ON jobs(runner_id);
+CREATE INDEX idx_jobs_definition ON jobs(job_definition_id);
+
+--------------------------------------------------------------------------------
+-- Job Log (append-only progress entries)
+--------------------------------------------------------------------------------
+
+CREATE TABLE job_log (
+    id         UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    job_id     UUID NOT NULL REFERENCES jobs(id) ON DELETE CASCADE,
+    timestamp  TIMESTAMPTZ NOT NULL DEFAULT now(),
+    level      TEXT NOT NULL DEFAULT 'info',
+    message    TEXT NOT NULL,
+    metadata   JSONB DEFAULT '{}'
+);
+
+CREATE INDEX idx_job_log_job ON job_log(job_id, timestamp);
+
+COMMIT;