Drop garbage uploads early (D42)

Random-named uploads that never get a real name or password were ~90% of
what seeding stores. Two filters:

- before storing (seeding, ingest): random-named uploads of a dropped
  signature (posting tool from the Message-ID, first group) or of a
  release dropped after its probe aren't stored; 2% of a dropped
  signature's releases are still kept and probed. Stored files of dropped
  signatures aren't probed.
- after a probe: a random-named release that is still unnamed, without
  password, names from files or spot, with all its probes done, and
  encrypted, a container or missing its first article, is deleted and
  tombstoned in dropped_releases.

Signatures are learned by gc:scheduler from a sample of probed releases
(signature_probes); garbage:learn --seed fills it from existing files.

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

commands/GcScheduler.ts

@@ -11,6 +11,8 @@ import StagingService from '#services/StagingService'
 import FilePartitions from '#services/FilePartitions'
 import ReleaseCompleteness from '#services/ReleaseCompleteness'
 import FileKeys from '#services/FileKeys'
+import GarbageFilter from '#services/GarbageFilter'
+import indexerConfig from '#config/indexer'
 import Shutdown from '#services/Shutdown'
 
 const CLEAN_BATCH = 1000
@@ -34,6 +36,8 @@ export default class GcScheduler extends BaseCommand {
 
   /** When release completeness was last recomputed (it runs less often than the sweep). */
   private completenessAt = 0
+  /** When the garbage signatures were last learned (D42). */
+  private learnedAt = 0
   /** When split uploads were last merged. */
   private mergedAt = 0
 
@@ -59,6 +63,11 @@ export default class GcScheduler extends BaseCommand {
         } catch (err: any) {
           this.logger.error(`file_keys fill failed: ${err.message}`)
         }
+        try {
+          await this.learnGarbage()
+        } catch (err: any) {
+          this.logger.error(`Garbage signatures failed: ${err.message}`)
+        }
         if (!this.once) await Shutdown.sleep(gcConfig.intervalMs)
       } while (!this.once && !Shutdown.requested)
     } finally {
@@ -155,6 +164,15 @@ export default class GcScheduler extends BaseCommand {
     if (checked > 0) this.logger.info(`Release completeness: ${checked} changed releases checked in ${Math.round((Date.now() - started) / 1000)} s.`)
   }
 
+  /** Learns which upload signatures are garbage from the probed releases (CONCEPT.md D42). */
+  private async learnGarbage() {
+    if (this.dryRun || (!this.once && Date.now() - this.learnedAt < indexerConfig.garbage.learnIntervalMs)) return
+    this.learnedAt = Date.now()
+    const { signatures, dropped, changed } = await GarbageFilter.learn()
+    this.logger.info(`Garbage signatures: ${dropped} of ${signatures} dropped.`)
+    for (const line of changed) this.logger.info(`Garbage signature ${line}`)
+  }
+
   private async rebuildIndexes() {
     const key = 'gc:reindex:last'
     const last = Number((await RedisService.client.get(key)) ?? 0)