The tail planner grows a group's open range; ranges:merge-tail packs the slivers

A round added a row a group whenever 100k articles or 15 minutes had passed,
tuned for a tail leased within minutes; with nothing leasing the tail the rows
piled up (127k planned tail ranges of a median 14k articles, 97% adjacent). Now
a round grows the group's last range when it is a planned, unspooled, untaken
row at the tail's priority, up to RANGE_ARTICLES, and only then adds rows; a
range taken meanwhile gets the slice as a row. ranges:merge-tail (--dry-run)
packs adjacent planned, uncaptured, unspooled, untaken tail ranges of a group
and priority into ranges of RANGE_ARTICLES under the lease lock.

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

commands/ranges_plan.ts

@@ -14,8 +14,13 @@ export default class RangesPlan extends BaseCommand {
 
   async run() {
     try {
-      const { groups, ranges } = this.tail ? await Planner.planTail() : await Planner.planAll()
-      this.logger.info(`${ranges} ${this.tail ? 'tail ' : ''}ranges planned over ${groups} groups.`)
+      if (this.tail) {
+        const { groups, ranges, extended } = await Planner.planTail()
+        this.logger.info(`Tail: ${ranges} ranges added, ${extended} grown, over ${groups} groups.`)
+      } else {
+        const { groups, ranges } = await Planner.planAll()
+        this.logger.info(`${ranges} ranges planned over ${groups} groups.`)
+      }
     } finally {
       await NntpPool.close()
     }