feat(ledger): mechanical proposer — every refresh proposes instances against canon and groups derive-first candidates; agents confirm in batches (#2792, milestone 294 step 6)

Shapes now carry a content fingerprint (signature + whitespace/comment-
insensitive body_sha; migration 0080) and the proposer runs inside the
coverage refresh, the one moment bodies exist: symbol elsewhere → textual
containment → body references the canon → signature resemblance → semantic
(capped per refresh, unreached rows stay unexamined for the next). A hit is
a proposal on the row (proposed_snippet_id/basis/score), never a
classification; rows with no canon hit group by the derive-first rule
(identical body in ≥2 places, same name in ≥3 files) as proposal_basis=
derive + a group key. list_shapes(proposal=any|canon|derive|<basis>) is the
queue; confirm_shape_proposals(project_id, snippet_id|path|basis) confirms
in batches as agent instances; any classify_shapes/hook stamp retires the
proposal. Readout carries proposed + derive_groups (line, payload, card).
Plugin 0.1.35 (skill: the machine proposes, judgment classifies).

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

frontend/src/views/ProjectView.vue

@@ -427,6 +427,13 @@ interface CoverageGap {
   unclassified: number;
   total: number;
 }
+interface DeriveGroup {
+  group: string;
+  kind: string;
+  label: string;
+  size: number;
+  paths: string[];
+}
 interface Coverage {
   total: number;
   accounted: number;
@@ -436,6 +443,10 @@ interface Coverage {
   computed_at: string;
   repos: { repo: string; ref: string; total: number; accounted: number }[];
   largest_gaps: CoverageGap[];
+  // The mechanical proposer's standing (#2792): canon proposals awaiting an
+  // agent's confirm, and the biggest repeats-with-no-canon families.
+  proposed?: number;
+  derive_groups?: DeriveGroup[];
 }
 
 const coverage = ref<Coverage | null>(null);
@@ -746,6 +757,24 @@ async function confirmDelete() {
               {{ gap.dir }} <span class="coverage-gap-count">{{ gap.unclassified }}</span>
             </span>
           </div>
+          <div
+            v-if="coverage.proposed || coverage.derive_groups?.length"
+            class="coverage-gaps"
+            title="The proposer matched these against canon; an agent confirms them in batches (confirm_shape_proposals)."
+          >
+            <span class="coverage-gaps-label">Proposed:</span>
+            <span v-if="coverage.proposed" class="coverage-gap-chip">
+              {{ coverage.proposed }} awaiting confirm
+            </span>
+            <span
+              v-for="g in coverage.derive_groups || []"
+              :key="g.group"
+              class="coverage-gap-chip"
+              :title="'Repeats with no canon — derive one first. ' + g.paths.join(', ')"
+            >
+              {{ g.label }} <span class="coverage-gap-count">×{{ g.size }}</span>
+            </span>
+          </div>
         </template>
         <p v-else class="coverage-empty">
           Not measured yet — Refresh reads the bound repo's definitions into