fix(sync): op_checkpoints pin write double-encodes jsonb — every sync aborts (#2339)

recordCompleted bound JSON.stringify(array) to a $3::jsonb param via postgres.js
.unsafe(), double-encoding it into a jsonb string scalar that violates the v119
op_checkpoints_completed_keys_array CHECK — aborting every multi-source sync on
real Postgres at the first checkpoint write. PGLite parses the string silently,
which is why unit tests stayed green and it shipped. Cast through $3::text::jsonb
so the text->jsonb cast parses a genuine array. Adds a DATABASE_URL-gated parity
test + a dedicated Postgres CI job so the guard can never silently skip.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.github/workflows/e2e.yml

@@ -20,6 +20,49 @@ concurrency:
   cancel-in-progress: true
 
 jobs:
+  jsonb-parity:
+    # Dedicated required guard for the JSONB double-encode bug-class (#2339).
+    # PGLite parses a double-encoded jsonb string silently, so this assertion can
+    # ONLY be made on real Postgres — a normal gated e2e file would skip without
+    # DATABASE_URL and let the bug ship green (as #2339 did). This job provisions
+    # Postgres and HARD-FAILS if DATABASE_URL is missing, so the guard can never
+    # silently skip.
+    name: JSONB parity (#2339 regression guard)
+    runs-on: ubuntu-latest
+    timeout-minutes: 15
+    services:
+      postgres:
+        image: pgvector/pgvector:pg16
+        env:
+          POSTGRES_USER: postgres
+          POSTGRES_PASSWORD: postgres
+          POSTGRES_DB: gbrain_test
+        ports:
+          - 5432:5432
+        options: >-
+          --health-cmd pg_isready
+          --health-interval 10s
+          --health-timeout 5s
+          --health-retries 5
+    steps:
+      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5  # v4
+      - uses: oven-sh/setup-bun@0c5077e51419868618aeaa5fe8019c62421857d6  # v2
+        with:
+          bun-version: 1.3.13
+      - run: bun install
+      - name: Require DATABASE_URL (no silent skip)
+        env:
+          DATABASE_URL: postgresql://postgres:postgres@localhost:5432/gbrain_test
+        run: |
+          if [ -z "$DATABASE_URL" ]; then
+            echo "::error::DATABASE_URL must be set for the jsonb-parity job — the #2339 guard would silently skip (the exact failure PGLite hides). Failing the job." >&2
+            exit 1
+          fi
+      - name: Run JSONB double-encode parity tests on real Postgres
+        env:
+          DATABASE_URL: postgresql://postgres:postgres@localhost:5432/gbrain_test
+        run: bun test test/e2e/op-checkpoint-jsonb-parity.test.ts test/e2e/jsonb-roundtrip.test.ts
+
   tier1:
     name: Tier 1 (Mechanical)
     runs-on: ubuntu-latest