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>

start/env.ts

@@ -74,6 +74,9 @@ export default await Env.create(new URL('../', import.meta.url), {
   SPOT_STANDALONE_AFTER_HOURS: Env.schema.number.optional(),
   CORPUS_AHEAD: Env.schema.number.optional(),
   PROBE_PIPELINE: Env.schema.number.optional(),
+  SNAPSHOT_DIR: Env.schema.string.optional(),
+  LEASE_MIN_PRIORITY: Env.schema.number.optional(),
+  LEASE_MAX_PRIORITY: Env.schema.number.optional(),
   PENDING_SHARE: Env.schema.number.optional(),
   PENDING_MIN_PROBES: Env.schema.number.optional(),
   PENDING_MAX_NAMED: Env.schema.number.optional(),