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>

edge/src/lease.rs

@@ -62,6 +62,8 @@ pub struct RulesJson {
     #[serde(default)]
     pub dropped_signatures: Vec<String>,
     #[serde(default)]
+    pub dropped_classes: Vec<String>,
+    #[serde(default)]
     pub dropped_tools: Option<Vec<String>>,
     #[serde(default)]
     pub per_article_max_parts: Option<u32>,
@@ -83,6 +85,7 @@ impl RulesJson {
         let mut rules = Rules::defaults(self.priorities.into_iter().collect());
         rules.version = self.version;
         rules.dropped_signatures = self.dropped_signatures.into_iter().collect();
+        rules.dropped_classes = self.dropped_classes.into_iter().collect();
         if let Some(tools) = self.dropped_tools {
             rules.dropped_tools = tools.into_iter().collect();
         }