Pending ladder by class, twins by content, dropped classes at the edge

The prober names 6% of the unnamed releases it finishes and the pending
queue (44M) grows eleven times faster than it probes. A sample of 44,530
finished pending rows shows the headers predict a name: size bucket, name
shape, completeness, tool and group separate 0% classes from 95% ones,
while the learner keyed on tool and group alone (LOG.md (130)).

- lib/release/classes.ts, names::pending_class, SQL pending_class():
  a release's class (size × shape × partial, 1..70), the three in step.
- Migration 6800: pending_releases.klass and target_bytes (the first
  target's article; candidates carry bytes now), pending_classes with
  each class's climbs, names, waiting and verdict, the claim's index.
- The ladder claims the classes with the best record first (a prior for
  the unexplored, at most a quarter of a claim from one), the cheapest
  target first within one, then the oldest of the rest; records classes
  like signatures and drops them at the same thresholds; discards their
  waiting releases. Claimed rows sorted in code: an UPDATE returns none.
- The rule set's droppedClasses: the edge keeps unnamed releases of a
  dropped class out of the pending store (counted as garbage), the
  explored sample excepted.
- hash_twins.ts: a probed file whose first 16 KiB and size match a named
  catalog release's names a pending release the probe didn't, and sets
  the inner name of a catalog release without one.
- pending:classes classes the rows from before and seeds the record from
  the finished ones; rules:classes publishes the dropped classes;
  releases:readable also marks the rows' candidates unreadable.

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

REBUILD.md

@@ -897,7 +897,20 @@ f. **Nothing enters the catalog without a usable name** (amended
    yields none counts against its signature, and a signature with
    ≥100 probes and ≤0.5% named (voyager 2's garbage learner, LOG.md
    2026-10-08 (5)) is **discarded** from then on, a sample of it still
-   probed to notice a change. The reason, in the 2016 replay: one poster's
+   probed to notice a change. **By class** (2026-11-02, LOG.md (130)): a
+   pending release's class is its tool, group, size bucket, name shape and
+   partial flag (`lib/release/classes.ts`, `names::pending_class`, the SQL
+   `pending_class()`; `pending_releases.klass`), and `pending_classes` keeps
+   each class's climbs and names; the claim takes the classes with the best
+   record first (`classScore`, a prior for the unexplored, at most a quarter
+   of a claim from one class), the cheapest target article first within one
+   (`target_bytes`), and the oldest of the rest; a class with the learner's
+   thresholds is dropped like a signature, and the rule set's
+   `droppedClasses` keep its releases out of the pending store at the edge,
+   the explored sample excepted. A probed file whose first 16 KiB and size
+   match a named catalog release's (`file_hashes`) takes that name without
+   another fetch (`app/services/hash_twins.ts`), on the ladder and for
+   catalog releases without one. The reason, in the 2016 replay: one poster's
    hash-named pieces ("Bob", 11 aliases, 3.2 M releases in five small
    groups) were 76% of the rows and three quarters of the NVMe bytes for
    11% of the segments and nothing anyone can find; the full history has