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>

start/env.ts

@@ -42,4 +42,15 @@ export default await Env.create(new URL('../', import.meta.url), {
   NNTP_USER: Env.schema.string.optional(),
   NNTP_PASSWORD: Env.schema.string.optional(),
   NNTP_SECURE: Env.schema.boolean.optional(),
+  NNTP_CONNECTIONS: Env.schema.number.optional(),
+  NNTP_TIMEOUT_MS: Env.schema.number.optional(),
+
+  // Coordinator
+  RANGE_ARTICLES: Env.schema.number.optional(),
+  CHUNK_ARTICLES: Env.schema.number.optional(),
+  LEASE_TTL_SECONDS: Env.schema.number.optional(),
+  SPOOL_DIR: Env.schema.string.optional(),
+  SPOOL_AHEAD_PER_LEASE: Env.schema.number.optional(),
+  SPOOL_MIN_AHEAD: Env.schema.number.optional(),
+  SPOOL_MAX_GB: Env.schema.number.optional(),
 })