Wave 7 chunk B: remove the embeddings machinery — the ladder collapses

The owner's wave-7 ruling: embeddings die entirely (git history is the
stash); clustering is birth-session derived (chunk A, 950ddfd), labels
are session names, and the prober's graph tools replace injection.

- settings: GraphSettings collapses to { enabled } — embedding,
  embeddingModel, clustering, labeling all die. Migration story: stale
  record keys are UNREAD and dropped by the sanitizer's reconstruction;
  the next graph-section PUT (replace-whole) persists the collapsed
  shape. The settings-panel GraphSection renders one master row.
- deleted: src/server/embeddings.ts (adapters, resolveEmbeddingPortFor,
  embedNewNodes, embeddingPort, embeddingModelCatalog), the
  GET /api/models/embeddings route, scripts/embed-graph.ts, tests for
  all three, and the /api/models/embeddings picker surfaces in the UI.
- prices: EMBEDDING_PRICES overlay + callCost fallback die. cost-summary:
  the embedding stage fold dies — back to three stages (extraction/
  audit/naming) per the owner ruling; historical stages.embedding spend
  in old run records is simply not displayed.
- ports: EmbeddingPort/EmbeddingResult/EmbeddingTask die. The embeddings
  LEDGER surface (readEmbeddings/writeEmbeddings + EmbeddingsLedger +
  EMBEDDINGS_FILE + graph-deletion's vector pruning) STAYS — inert data,
  kept only so graph-context.ts compiles until Teacher's pass removes
  it; the seam dies in the follow-up interlude.
- chat-handler (approved cross-lane unwiring, wave-6 precedent): the
  extraction pipeline's embedder becomes a documented no-op (nothing
  embedded, nothing spent, ledger untouched) until Teacher's pass
  removes the phase; the graph-context injection dispatch gate, the
  graphContext deps wiring, the setContextRespawn seam, and
  turn-service's triggerGraphContext are gone — injection is dead
  code pending Teacher's file deletions.
- scripts: backfill-graph/import-notes pass the same no-op embedder;
  replay-layout derives clusters from birthSessionPartition (the same
  partition the real settle uses) instead of the embeddings ledger.
- settings-body: parseGraphSettingsBody reads the master switch only —
  old-shape keys in a body are ignored, not rejected; bad shapes 400.
- next.config: the @huggingface tracing-exclusion guards die with the
  last reference.

Cross-lane flags: extraction.ts/graph-context.ts keep stale embed
comments + the embed phase until Teacher's full pass (their parallel
interlude owns those files — zero overlap kept by design);
semantic-clusters.ts + its test stay one more round (extraction.test.ts,
Teacher's file, still imports it — they delete it with the namer cases);
ChatSettings.graphContextTokens + the graph-context-control UI stay
until Teacher+UI.

Gates: tsc clean, eslint clean, 885/885 tests, build compiles.
Live-verified on the port-3004 dev tree: PUT /api/settings/graph with
dead keys collapses on write, bad shapes 400, GET reads {enabled: true},
/api/models/embeddings 404s.

scripts/replay-layout.ts

@@ -18,6 +18,7 @@ const depthArg = process.argv.find((a) => a.startsWith("--depth="));
 const depthMode: "off" | "vertical" | "radial" =
 	depthArg === "--depth=vertical" ? "vertical" : depthArg === "--depth=radial" ? "radial" : "off";
 import { incrementalLayout } from "../src/core/layout.ts";
+import { birthSessionPartition } from "../src/core/session-clusters.ts";
 import type { GraphNode, NodeMapping, Position } from "../src/core/contracts.ts";
 
 function main() {
@@ -32,12 +33,9 @@ function main() {
 		nodes.push(line);
 	}
 	const edges = graphStore.readEdges();
-	// The semantic-topic source: the embedding ledger (run
-	// scripts/embed-graph.ts first if missing/stale).
-	const embeddings = graphStore.readEmbeddings();
-	if (Object.keys(embeddings.vectors).length === 0) {
-		console.warn("[replay] embedding ledger is empty — clusters will be absent (run scripts/embed-graph.ts)");
-	}
+	// The cluster source (wave 7): the birth-session partition, derived on
+	// read — same as the real settle (core/layout-settle.ts).
+	const birthClusters = birthSessionPartition(nodes);
 
 	// Batches: each imported file, in real import order (sources.json
 	// importedAt). A node belongs to the file whose mapping first claims it
@@ -85,9 +83,8 @@ function main() {
 		const batchNodes = nodes.filter((n) => delivered.has(n.id));
 		positions = incrementalLayout(batchNodes, activeEdges, positions, {
 			// The same partition the real settle would see for this batch:
-			// the persisted semantic topics, filtered to delivered nodes
-			// (never recomputed — the agglomerative pass is ~1.5s at scale).
-			clusters: embeddings.clusters
+			// the birth-session clusters, filtered to delivered nodes.
+			clusters: birthClusters
 				.map((c) => ({ members: c.members.filter((id) => delivered.has(id)) }))
 				.filter((c) => c.members.length > 0),
 			...(depthMode === "off"