Rebuild: coordinator (planner, NNTP pool, spool, prefetcher, leases, rule sets), node API and the edge:node worker

- groups:add / ranges:plan / nodes:create / coordinator:run commands
- the node API: lease, the range's chunks as one framed stream from the
  spool, batches, heartbeat, finish, release (node guard, token per node)
- edge:node: needs COORDINATOR_URL and NODE_TOKEN only (placeholders for
  the rest), posts a batch every 10 chunks, gives its range back on SIGTERM
- releases are gathered per batch: 1.04 chunk rows per release at 10
  chunks per batch (1.35 when built per XOVER chunk)
- partitions are checked per batch instead of remembered

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

app/services/chunk_partitions.ts

@@ -7,15 +7,14 @@ const AHEAD = 2
 /**
  * release_chunks is partitioned by month of writing (REBUILD.md, decision a).
  * Inserts fail without a partition for now(), so the current and the next
- * months' partitions are created before they are needed; checked once per
- * process and month.
+ * months' partitions are created before they are needed.
  */
 class ChunkPartitions {
-  private ensuredFor: string | null = null
-
   async ensure(now = new Date()) {
-    const month = now.toISOString().slice(0, 7)
-    if (this.ensuredFor === month) return
+    // Checked each time, not remembered: a rolled-back transaction can take a created partition along.
+    const current = `release_chunks_${now.toISOString().slice(0, 7).replace('-', '')}`
+    const { rows } = await db.rawQuery(`SELECT to_regclass(?) IS NOT NULL AS present`, [current])
+    if (rows[0].present) return
     const tablespace = env.get('CHUNK_TABLESPACE')
     for (let i = 0; i <= AHEAD; i++) {
       const from = new Date(Date.UTC(now.getUTCFullYear(), now.getUTCMonth() + i, 1))
@@ -25,7 +24,6 @@ class ChunkPartitions {
         `CREATE TABLE IF NOT EXISTS ${name} PARTITION OF release_chunks FOR VALUES FROM ('${from.toISOString()}') TO ('${to.toISOString()}')${tablespace ? ` TABLESPACE ${tablespace}` : ''}`
       )
     }
-    this.ensuredFor = month
   }
 }