The window worker: group leases, the stream serving the corpus, the snapshot through the API (design 1 and 5)

A worker thread leases a group and takes its ranges in article order through
one carried window; the coordinator keeps one cursor a group (group_leases,
migration 6500) and hands out the next range, the rules and nothing about
where the chunks are: the range stream serves a stored range's chunks from the
corpus file and a live one's from the spool. The window's snapshot (bincode:
the frontier, the open files, releases and albums, the upload numbers, the
batch-counter table) goes to the coordinator every EDGE_SNAPSHOT_MINUTES and
when the group is given back, and the next holder restores it; a takeover
after LEASE_TTL_SECONDS plans the ranges from the snapshot's article again.
The prefetcher runs ahead of held groups' cursors and skips chunks the corpus
has. LEASE_MIN_PRIORITY..LEASE_MAX_PRIORITY bound what is leased. edge-node
holds groups by default; --ranges keeps the old per-range path.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

database/migrations/1770000006500_group_leases.ts

@@ -0,0 +1,33 @@
+import { BaseSchema } from '@adonisjs/lucid/schema'
+
+/**
+ * Group leases (REBUILD.md, "Voyager 3: window indexing", 1 and 5; 2026-10-26): a worker thread holds a group, not
+ * a range, and indexes its ranges in article order through one carried window. One row a group: the holder and
+ * its heartbeat, the range it works, and the snapshot of its window (the article it stands at: the next one to
+ * index) that the coordinator keeps on bulk. Ranges stay what is planned, fetched and finished.
+ */
+export default class extends BaseSchema {
+  async up() {
+    this.schema.raw(`
+      CREATE TABLE group_leases (
+        group_id integer PRIMARY KEY REFERENCES groups (id) ON DELETE CASCADE,
+        -- The holder; null between holders. A holder quiet for LEASE_TTL_SECONDS is taken over.
+        node_id integer,
+        leased_at timestamptz,
+        heartbeat_at timestamptz,
+        -- The range the holder works (null between ranges).
+        range_id bigint,
+        -- The window's snapshot: the article it stands at (a resume point), and when it was taken; null: none.
+        snapshot_next bigint,
+        snapshot_at timestamptz,
+        ranges_done integer NOT NULL DEFAULT 0,
+        headers bigint NOT NULL DEFAULT 0,
+        created_at timestamptz NOT NULL DEFAULT now()
+      )`)
+    this.schema.raw(`CREATE INDEX group_leases_held_idx ON group_leases (heartbeat_at) WHERE node_id IS NOT NULL`)
+  }
+
+  async down() {
+    this.schema.raw(`DROP TABLE IF EXISTS group_leases`)
+  }
+}