Clusters phases B+C: labeling records, the naming call, snapshot payload

Core-survival labelings (vision section 1, DECIDED 2026-09-13):
ClusterLabeling records in a new append-only ledger
(data/graph/cluster-labels.jsonl), immutable, id = clu_ + sha256 of the
sorted core so re-naming races and re-runs dedupe at the store seam.
matchClusterLabelings (core/clusters.ts, pure): a community keeps a
record's label while at least half its core survives in it; both sides
single-successor (a split keeps one name; greedy by overlap, ties to
the newer record).

The namer (src/agent/subagents/cluster-namer.ts): ONE singular cheap LLM
call (new 'labeler' role, glm-flash/low) names every new/changed
community at once, given member names + statements (capped at 12
members per cluster). refreshClusterLabels runs POST-EXTRACTION
(user-decided) from both front doors, fire-and-forget — naming failure
never fails the run; refreshes serialize behind a chain so parallel
imports never mint duplicate labels. import-notes.ts awaits
clusterNamingSettled before exit.

Payload: GraphSnapshot.clusters (>= MIN_CLUSTER_SIZE 3) joins detection
with labelings at read time — claimed clusters carry the record's label
and id; unlabeled ones carry a member-hash id and null label. Detection
is deterministic so no memo in v1 (ms at current scale; revisit at
vault scale).

Tests (372/372): matcher half-rule/split/merge/greedy/tie cases; naming
end-to-end through importNotes (one call, one record, claim on
re-refresh), naming failure non-fatal; snapshot derivation with
labeling join; 11 test pipelines now pin an explicit labeler seam.

src/agent/subagents/extraction.ts

@@ -16,6 +16,7 @@ import type {
 	SessionFindings,
 } from "../../core/contracts.ts";
 import { getGraph, mergeFindings, type EmissionStats, type GraphDeps } from "../../core/graph.ts";
+import { refreshClusterLabels } from "./cluster-namer.ts";
 
 /**
  * The extraction pipeline (vision §1 construction, 2026-09-02 redesign) — the
@@ -548,6 +549,8 @@ export interface ExtractionModels {
 	/** Test seam: a scripted engine per stage (production uses the roles). */
 	extractor?: PiEngine;
 	auditor?: PiEngine;
+	/** Test seam for the cluster namer (post-extraction garnish). */
+	labeler?: PiEngine;
 }
 
 export interface ExtractionPipelineDeps extends GraphDeps, ExtractionModels {}
@@ -716,6 +719,13 @@ export function createExtractionPipeline(deps: ExtractionPipelineDeps): Extracti
 				`[extraction ${chatId}] merged: ${stats.nodes} nodes, ${stats.edges} edges, ${stats.events} events ` +
 					`(${Math.round(performance.now() - t0)}ms total)`,
 			);
+			// Post-extraction garnish (DECIDED 2026-09-13): name new/changed
+			// clusters. Fire-and-forget — naming never fails the run.
+			refreshClusterLabels({
+				graphStore,
+				engine: deps.labeler,
+				signal: runningExtractions.get(chatId)?.controller.signal,
+			}).catch(() => {});
 			return stats;
 		} catch (err) {
 			persistRunUsage(chatId, Math.round(performance.now() - t0), undefined);
@@ -819,6 +829,11 @@ export function createExtractionPipeline(deps: ExtractionPipelineDeps): Extracti
 				`[extraction ${id}] merged: ${stats.nodes} nodes, ${stats.edges} edges, ${stats.events} events ` +
 					`(${Math.round(performance.now() - t0)}ms total)`,
 			);
+			refreshClusterLabels({
+				graphStore,
+				engine: deps.labeler,
+				signal: runningExtractions.get(id)?.controller.signal,
+			}).catch(() => {});
 			return stats;
 		} catch (err) {
 			persistRunUsage(id, Math.round(performance.now() - t0), undefined);