Graph redesign: true propositions, follows/supports, auditor-owned identity (vision §1 minimal implementation)

The minimal implementation of the 2026-09-02 graph vision (docs/vision.md §1):

- contracts/graph.ts: every node is a TRUE proposition (statement is both
  rendering label and identity key; required description; no kind, no name).
  Edges are follows (derivable) / supports (grounds without entailing) with
  message-granular provenance points {chatId, messageId}. Events reduce to
  correct/miss/dont-know plus observation (understanding notes); no taught
  events, no misconception kind.
- extraction.ts: extractor is TREE-BLIND (transcript only, no plan tree) and
  free-form; auditor sees findings + the current graph, owns faithfulness and
  identity (link-or-create verdict per proposition, recorded as linkTo);
  transcriptView tags every line with its message id (provenance anchors).
- core/graph.ts merger: applies verdicts deterministically — linkTo appends
  a link line (phrasings join aliases, provenance unions; reads merge by id),
  absent creates; NO string matching anywhere. Quiz events rebuilt from tool
  parts with attribution-only nodeId resolution; understanding notes become
  observation events (obs:<sourceId>); mapping lines are the verdict audit
  trail and make re-merges idempotent.
- deriveNodeStates: transitional — latest quiz event wins (known/missed/
  dont-know, else candidate); taught unreachable until the state-model
  ideation lands.
- graph-context.ts + 50-graph-context.md: follows chains, hotspot grouping,
  state vocabulary updated for the new event kinds.
- graph-view.tsx: node label is the statement; detail shows statement +
  description.
- tests: merger verdicts (link, no-string-match, cross-chat assertions),
  tree-blind pipeline end-to-end, follows vocabulary in context tests.
  276/276 green.

components/graph-view.tsx

@@ -363,7 +363,7 @@ export function GraphView() {
 			// frozen layout stable for a given node set across remounts.
 			const rand = seededRandom(node.id);
 			graph.addNode(node.id, {
-				label: node.name,
+				label: node.statement,
 				size: STATE_TOKENS[state].size,
 				color: stateColors.get(state) ?? edgeColor,
 				x: (rand() - 0.5) * 100,
@@ -552,8 +552,8 @@ export function GraphView() {
 					style={{ visibility: "hidden", left: 0, top: 0 }}
 					className="absolute z-10 w-80 max-w-[calc(100%-1rem)] rounded-xl border bg-card p-4 text-left shadow-lg"
 				>
-					<div className="text-sm font-medium leading-snug">{selected.node.name}</div>
-					<div className="mt-1 text-xs leading-relaxed text-muted-foreground">{selected.node.statement}</div>
+					<div className="text-sm font-medium leading-snug">{selected.node.statement}</div>
+					<div className="mt-1 text-xs leading-relaxed text-muted-foreground">{selected.node.description}</div>
 					<div className="mt-1 text-xs uppercase tracking-wide text-muted-foreground">
 						{STATE_LABELS[selected.state]}
 					</div>