chains-primary: stored chains replace typed edges; edges become a derived view

Owner rulings 2026-09-30: reasoning chains are the stored truth; the graph
canvas renders a lossy derived image. No migration, no backcompat — old
graph data was wiped.

- contracts: GraphChain (arg_-minted id, premises, conclusion) replaces
  typed edges; GraphEdge survives only as the untyped derived arrow;
  GraphSnapshot carries stored chains; supports edges retired entirely
- store: chains.jsonl ledger (edges.jsonl purged at load alongside legacy
  events.jsonl); readChains/appendChain seam; merge dedupes by
  (sorted premises, conclusion), re-assertions append under the same arg_ id
- core: deriveView mints implication nodes (name ⟹, statement via
  formatChainLine) plus premise→imp→conclusion arrows; clusters stay
  proposition-only (birthSessionPartition); chainsForSelection now groups
  STORED chains (chain rides iff every member selected) — independent
  arguments for one conclusion never union; chainsToGraph/chainsToEdges die
- extraction: extractor submits chains natively (expandFindings deleted);
  auditor receives propositions only; supports fan-out gone
- deletion: full death of a proposition kills every referencing chain;
  arg_-prefixed node deletes kill that chain; chainsRemoved stats
- UI: every arrow renders the ⟹ double shaft; supports toggle + thickness
  slider and detail-card edge sections deleted (card keeps name +
  proposition); chain table + practice pipeline read stored chains
- tests: 1188 green across the new seams

scripts/import-notes.ts

@@ -33,7 +33,7 @@ async function main() {
 		getChunkTokens: () => effectiveSettings().graph.extractionChunkTokens,
 	});
 	const queue = [...files];
-	const totals = { nodes: 0, edges: 0, failed: 0 };
+	const totals = { nodes: 0, chains: 0, failed: 0 };
 	const workers = Array.from({ length: Math.min(limit, files.length) }, async () => {
 		for (;;) {
 			const file = queue.shift();
@@ -43,9 +43,9 @@ async function main() {
 			try {
 				const stats = await pipeline.importNotes({ filePath, text: fs.readFileSync(filePath, "utf-8") });
 				totals.nodes += stats.nodes;
-				totals.edges += stats.edges;
+				totals.chains += stats.chains ?? 0;
 				console.log(
-					`[import-notes] ${file}: ${stats.nodes} nodes, ${stats.edges} edges in ${((Date.now() - t0) / 1000).toFixed(1)}s`,
+					`[import-notes] ${file}: ${stats.nodes} nodes, ${stats.chains ?? 0} chains in ${((Date.now() - t0) / 1000).toFixed(1)}s`,
 				);
 			} catch (err) {
 				totals.failed++;
@@ -57,8 +57,8 @@ async function main() {
 
 	const graph = getGraph(stores.graphStore);
 	console.log(
-		`[import-notes] done: +${totals.nodes} nodes, +${totals.edges} edges, ${totals.failed} failed — ` +
-			`graph now ${graph.nodes.length} nodes, ${graph.edges.length} edges`,
+		`[import-notes] done: +${totals.nodes} nodes, +${totals.chains} chains, ${totals.failed} failed — ` +
+			`graph now ${graph.nodes.length} nodes, ${graph.chains.length} chains`,
 	);
 }