delete the mappings ledger — per-job in-memory resolution + notes fingerprint guard

The persisted (chatId, sourceId)→node table was a shared namespace across
independent chunk/batch jobs: each chunk's extractor mints local ids fresh
(p1..pN), so later chunks collided with earlier ones — propositions silently
skipped as 'already resolved' (coverage checkpointed anyway: permanent silent
loss) and edges resolved onto the wrong nodes (the 'everything links to
everything' mush). Owner ruling 2026-09-29: mergeFindings resolves THIS job's
ids in memory, nothing persists between jobs; cross-job identity is the
auditor's linkTo verdicts alone.

- contracts: NodeMapping dies; NotesSource.contentFp — sha256 of the text at
  the last run, the re-import guard (unchanged re-import = TRUE no-op, no
  model calls, no usage; changed text re-runs; legacy unstamped sources
  re-run once)
- merger: job-local resolution map, in-submit duplicate ids skip once,
  edges resolve extractor-local ids only
- ports/store: appendMapping/readMappings, LEDGER_FILES.mappings,
  rewriteLedgers.mappings gone (stale data/graph/mappings.jsonl just stops
  being read)
- session-clusters: birthSessionOf is provenance-only — the legacy
  mapping-line fallback for provenance-empty notes nodes dies
- deletion: no mapping rows to strip; stats lose mappingsRemoved
- replay-layout batches nodes by first provenance point
- graph.test pins the new independence semantics (re-merge re-creates;
  duplicate ids within one submit resolve once); extraction tests pin
  per-chunk merges + the fingerprint guard

tests/graph-tools.test.ts

@@ -37,14 +37,12 @@ function fakeStores(
 	nodes: GraphNode[],
 	over: {
 		chats?: Array<Pick<ChatSummary, "id" | "title" | "createdAt" | "updatedAt">>;
-		mappings?: Array<{ chatId: string; sourceId: string; graphNodeId: string }>;
 	} = {},
 ): { chatStore: ChatStore; graphStore: GraphStore } {
 	const edges: GraphEdge[] = [];
 	const graphStore: GraphStore = {
 		readNodes: () => nodes,
 		readEdges: () => edges,
-		readMappings: () => over.mappings ?? [],
 		readCheckpoints: () => [],
 		readCoverage: () => [],
 		readSources: () => [],
@@ -217,12 +215,7 @@ describe("auditor graph tools", () => {
 	});
 
 	it("list_propositions: FULL statement text (identity work), no dates", async () => {
-		const { chatStore: cs, graphStore: gs } = fakeStores(nodes, {
-			mappings: [
-				{ chatId: "c1", sourceId: "p1", graphNodeId: "n1" },
-				{ chatId: "c1", sourceId: "p2", graphNodeId: "n2" },
-			],
-		});
+		const { chatStore: cs, graphStore: gs } = fakeStores(nodes);
 		const tools = auditorGraphTools({ chatStore: cs, graphStore: gs });
 		const out = (await tools.list_propositions!.execute!("tc", { session: "c1" })).details as string;
 		assert.match(out, /2 proposition\(s\) born in this session:/);