feat(ledger): divergence readout — button B where button A is canon, shape history, and judged-shape recheck (#2793, milestone 294 step 7)

Every judgment now goes through one helper that remembers the fingerprint
judged (classified_sha) and writes a code_shape_events row; the sync writes
vanished / reappeared / drifted events and flags recheck_at when a body
moves under an instance/variant. The refresh flags diverges_from on shapes
new since the previous computation that sit where one canon dominates the
judged siblings of their directory+kind and were not proposed as that canon
(a first seed flags nothing); the write-path hint asks the same question
in-band for the shapes the hook names. list_shapes(flag=divergence|recheck),
shape_history(project_id, path, symbol) (read-only), coverage line/payload/
card carry divergent + recheck. Backup v8 carries the history. Plugin 0.1.36.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

plugin/skills/shape-accounting/SKILL.md

@@ -80,6 +80,25 @@ the dominant form, `create_snippet` it, migrate the outliers, then classify
 the rest as instances. Canon is determined from the code; consistency comes
 from the derivation, not from asking permission.
 
+## The divergence readout — button B where button A is canon
+
+Three questions the ledger answers mechanically (#2793):
+
+- **Divergence** — `list_shapes(project_id, flag="divergence")` (and the
+  coverage line's "N DIVERGENT"): a shape new since the previous refresh, in
+  a directory where one canon dominates the judged siblings, that the
+  proposer did not match to that canon. `diverges_from` names the canon.
+  Judge it: `instance` if it should be built from the canon (and rebuild
+  it), `variant` with the why if the departure is deliberate. The write-path
+  hook asks the same question in-band the moment such a shape is written.
+- **History** — `shape_history(project_id, path, symbol?)`: the current rows
+  plus every `classified` / `vanished` / `reappeared` / `drifted` event with
+  its commit — "instance of #N from <date>, re-judged variant of #M because
+  R, vanished at C". Rows, not recollection.
+- **Recheck** — `list_shapes(project_id, flag="recheck")`: judged
+  instances/variants whose body changed since judged. The judgment stands;
+  re-confirm it (classify again with the same status) or re-judge.
+
 ## What this buys
 
 Divergence becomes mechanical: when button B appears where button A is canon,