feat(workers): pgboss claim/complete/fail via psycopg

Adds the Boss class — SELECT … FOR UPDATE SKIP LOCKED to atomically
claim, UPDATE state on completion. Retry semantics match pg-boss:
exponential backoff via retry_count / retry_delay / retry_backoff.

Forces client_encoding=UTF8 on every connection. The void2-db cluster
was initialized as SQL_ASCII so psycopg refuses to decode text by
default; UTF8 client_encoding works because the data is already UTF-8.
Node's pg lib is more forgiving and didn't surface this.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

workers/tests/conftest.py

@@ -0,0 +1,43 @@
+import os
+import pytest
+import psycopg
+
+DB_URL = os.environ["DATABASE_URL"]
+
+@pytest.fixture
+def conn():
+    with psycopg.connect(DB_URL, autocommit=True, client_encoding='UTF8') as c:
+        yield c
+
+@pytest.fixture(autouse=True)
+def reset_pgboss(conn):
+    """Drop the pgboss schema before each test. Tests that need it call ensure_pgboss(conn)."""
+    conn.execute("DROP SCHEMA IF EXISTS pgboss CASCADE")
+    yield
+
+def ensure_pgboss(conn):
+    """Bring up a minimal pgboss schema matching the columns boss.py reads/writes."""
+    conn.execute("CREATE SCHEMA IF NOT EXISTS pgboss")
+    conn.execute("""
+      CREATE TABLE IF NOT EXISTS pgboss.job (
+        id uuid PRIMARY KEY DEFAULT gen_random_uuid(),
+        name text NOT NULL,
+        priority int NOT NULL DEFAULT 0,
+        data jsonb,
+        state text NOT NULL DEFAULT 'created',
+        retry_limit int NOT NULL DEFAULT 5,
+        retry_count int NOT NULL DEFAULT 0,
+        retry_delay int NOT NULL DEFAULT 10,
+        retry_backoff boolean NOT NULL DEFAULT true,
+        start_after timestamptz NOT NULL DEFAULT now(),
+        started_on timestamptz,
+        completed_on timestamptz,
+        created_on timestamptz NOT NULL DEFAULT now(),
+        output jsonb
+      )
+    """)
+
+@pytest.fixture
+def boss_ready(conn):
+    ensure_pgboss(conn)
+    yield conn