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>

edge/src/lease.rs

@@ -11,6 +11,40 @@ pub struct LeaseJson {
     pub rules: RulesJson,
 }
 
+/// A group lease (lib/edge/lease.ts GroupLease): the group a worker thread holds, the rules, the window's snapshot if any.
+#[derive(Deserialize)]
+pub struct GroupLeaseJson {
+    pub group: GroupJson,
+    pub rules: RulesJson,
+    pub snapshot: Option<SnapshotJson>,
+}
+
+#[derive(Deserialize)]
+pub struct GroupJson {
+    pub id: i64,
+    pub name: String,
+    pub priority: i64,
+}
+
+#[derive(Deserialize)]
+pub struct SnapshotJson {
+    pub next: i64,
+}
+
+/// The group's next range (lib/edge/lease.ts NextRange).
+#[derive(Deserialize)]
+pub struct NextRangeJson {
+    pub range: RangeSpanJson,
+}
+
+#[derive(Deserialize, Clone, Copy)]
+pub struct RangeSpanJson {
+    pub id: i64,
+    pub start: i64,
+    pub end: i64,
+    pub next: i64,
+}
+
 #[derive(Deserialize)]
 pub struct RangeJson {
     pub id: i64,