fix: chain table reads the stored propositions, not the derived canvas image

The owner's live test surfaced it: after importing notes, the chains view
listed implication nodes as bogus singleton "chains" — and each carried
the same arg_ id as the real stored chain, tripping React's duplicate-key
error (chain-table.tsx:372).

Root cause: graph-view passed snapshot.nodes — the derived canvas view
(propositions + implication nodes) — into ChainTableOverlay, whose
chainsForSelection turns every unchained node into a singleton chain.
An implication node is never a chain member (members are proposition
ids), so every imp node minted a bogus singleton with a colliding id;
its row was even selectable, leaking arg_ ids into practice input.

Fix (owner-approved shape): GraphSnapshot gains `propositions` — the
stored-truth node list riding beside `chains` for exactly this class of
consumer. The chain table now receives snapshot.propositions; the canvas
keeps snapshot.nodes (imp nodes are meant to be drawn). Practice pipeline
unaffected (it already read getGraph, which is propositions-only).

Test: the snapshot split pinned as an invariant in graph.test.ts — image
= truth + one imp node per fully-live stored chain; truth never carries
an arg_ id.

components/graph-view.tsx

@@ -1656,7 +1656,7 @@ export function GraphView() {
 			    here.) */}
 			<ChainTableOverlay
 				open={chainsOpen && !isEmpty}
-				nodes={snapshot?.nodes ?? []}
+				nodes={snapshot?.propositions ?? []}
 				chains={snapshot?.chains ?? []}
 				sessions={snapshot?.sessions ?? {}}
 				fileSources={snapshot?.fileSources ?? {}}

src/core/contracts/graph.ts

@@ -307,6 +307,10 @@ export interface GraphSnapshot {
 	/** Proposition nodes + the DERIVED implication nodes (one per chain,
 	 *  id = chain id) — what the canvas renders. */
 	nodes: GraphNode[];
+	/** The STORED proposition nodes alone (no derived implication nodes)
+	 *  — the stored truth, like `chains`: consumers that read the world
+	 *  (the chain table) take this list, never the canvas image. */
+	propositions: GraphNode[];
 	/** DERIVED untyped arrows: premise → imp → conclusion. A lossy image
 	 *  of the stored chains — rebuilt after every change, never stored. */
 	edges: GraphEdge[];

src/core/graph.ts

@@ -409,6 +409,7 @@ export function graphSnapshot(deps: GraphDeps): GraphSnapshot {
 
 	return {
 		nodes,
+		propositions: graph.nodes,
 		edges: view.edges,
 		chains: graph.chains,
 		sessions,

tests/graph.test.ts

@@ -457,6 +457,20 @@ describe("the merger (mergeFindings)", () => {
 		assert.ok(mine, "the trio is one cluster");
 		assert.equal(mine!.id, "src_clusterfixture");
 		assert.equal(mine!.label, "/vault/cluster notes.md", "a notes file is a birth-session — the label is its path");
+
+		// Chains-primary split (owner, 2026-09-30): `nodes` is the canvas
+		// image (propositions + derived implication nodes), `propositions`
+		// is the stored truth alone — the chain table's input. The store is
+		// shared across this suite, so assert the INVARIANT, not counts:
+		// image = truth + one imp node per fully-live stored chain, and the
+		// truth never carries an arg_ id.
+		const stored = graphStore.readChains();
+		const live = new Set(snap.propositions.map((n) => n.id));
+		const liveChains = stored.filter((c) => live.has(c.conclusion) && c.premises.every((p) => live.has(p)));
+		assert.ok(snap.propositions.every((n) => !n.id.startsWith("arg_")), "the stored-truth list never carries imp nodes");
+		assert.equal(snap.nodes.length, snap.propositions.length + liveChains.length, "image = truth + one imp node per live chain");
+		const imp = snap.nodes.filter((n) => n.id.startsWith("arg_"));
+		assert.ok(imp.length === liveChains.length && imp.every((n) => snap.propositions.every((p) => p.id !== n.id)), "the extra nodes are exactly the derived implication nodes");
 	});
 
 	it("derives the sessions index in graphSnapshot", () => {