Rebuild: merger rounds with one neighbour query, a cursor and a time budget; planning skips failing groups

The neighbour check was three queries per file (~2,000 files/minute); now
one per round of 20k files, with a cursor so waiting files don't take
every round's places, and rounds until nothing is left or 30 s. On the
dev backlog (old-style fragments): ~18k files/minute in the 30 s budget;
at full throughput the new fragment rule leaves ~1,200 files/minute.
A group that fails GROUP (gone from the server) no longer stops planning
the others; edge:bench's groups are inactive.

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

app/services/planner.ts

@@ -1,4 +1,5 @@
 import db from '@adonisjs/lucid/services/db'
+import logger from '@adonisjs/core/services/logger'
 import coordinatorConfig from '#config/coordinator'
 import NntpPool from '#services/nntp_pool'
 
@@ -56,7 +57,14 @@ class Planner {
   async planAll(): Promise<{ groups: number; ranges: number }> {
     const groups = await db.from('groups').where('active', true).orderBy('priority').select('id', 'name')
     let ranges = 0
-    for (const group of groups) ranges += await this.planGroup({ id: Number(group.id), name: group.name })
+    for (const group of groups) {
+      // One group failing (e.g. gone from the server) doesn't stop the others.
+      try {
+        ranges += await this.planGroup({ id: Number(group.id), name: group.name })
+      } catch (error: any) {
+        logger.warn(`Planning ${group.name}: ${error.message}`)
+      }
+    }
     return { groups: groups.length, ranges }
   }
 }