Seed plans fill every uncovered gap, with priorities; cheaper ingest and file storing

- seed:plan plans every part of a group's history no range covers (it
  started below the lowest known range and left a.b.ath's 13 most recent
  months out); seed_ranges.priority orders leases (seed:plan --priority).
- binaries.part_count, kept by the parts insert in the same statement:
  claimCompleted compares it instead of counting parts every batch.
- file_keys: 64-bit hashes of all file keys; FileStore.insert asks it
  before probing every files partition.
- worker:file stores 100 completed binaries per job with set-based queries.

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

commands/SeedPlan.ts

@@ -4,9 +4,10 @@ import NntpService from '#services/NntpService'
 import SeedOrchestrator from '#services/SeedOrchestrator'
 
 /**
- * Plans seed ranges (CONCEPT.md D38) for groups, from below what live
- * indexing, the backfill and earlier plans cover down to `--days` back (or
- * the server's oldest article). A group's backfill stops where its plan
+ * Plans seed ranges (CONCEPT.md D38) for groups: every article from below
+ * what live indexing and the backfill cover down to `--days` back (or the
+ * server's oldest article) that no earlier range covers. Running it again
+ * plans only what's missing. A group's backfill stops where its plan
  * starts. Ranges are interleaved across groups, newest first.
  *
  *   node ace seed:plan alt.binaries.ath alt.binaries.mom --days 365
@@ -28,11 +29,16 @@ export default class SeedPlan extends BaseCommand {
   @flags.number({ description: 'Articles per range', default: 2_000_000 })
   declare size: number
 
+  @flags.number({ description: 'Leased before ranges of a lower priority (default 0)', default: 0 })
+  declare priority: number
+
   public async run() {
     try {
-      const summary = await SeedOrchestrator.plan(this.groups, { days: this.days, size: this.size })
+      const summary = await SeedOrchestrator.plan(this.groups, { days: this.days, size: this.size, priority: this.priority })
       for (const s of summary) {
-        this.logger.info(`${s.group}: ${s.ranges.toLocaleString('en')} ranges, articles ${s.from.toLocaleString('en')}–${s.to.toLocaleString('en')}.`)
+        this.logger.info(
+          `${s.group}: ${s.ranges.toLocaleString('en')} new ranges in ${s.gaps} gap(s) not yet planned, articles ${s.from.toLocaleString('en')}–${s.to.toLocaleString('en')}.`
+        )
       }
     } finally {
       await NntpService.shutdown()