feat: graph context injection — the session's prior knowledge, steered in at session start (vision-context-injection.md)

One shot per chat, fired at the first turn's onFinish: the session's
topic (its only typed message) is embedded as an EmbeddingGemma retrieval
query; the semantically closest graph propositions are selected under the
session's token budget (pure budget, no similarity threshold — the
decided doctrine) and delivered as a marker-only steer through the wake
pipeline, queuing behind pending questions like every sub-agent result.

- contracts: ChatSettings.graphContextTokens (default 1024, max 4096,
  step 128, 0 = off); GraphContextData + graphContextText; the
  graph-context JobKind + buildGraphContextSteer (id steer_ctx_<chatId>)
- core/graph-context.ts: brute-force cosine top-K, greedy chars/4 fill
  under budget, most-recent UnderstandingLevel fold, count cap 64,
  parse-don't-cast at the marker seam
- server: embedQuery (role-asymmetric query format, same warm singleton
  — vector-space parity by construction); the runner (startGraphContext-
  Injection one-shot gates; runGraphContextJob validates ledger parity);
  wake branches (chatIdOf/jobIdOf, finalizeJob done, recoverStaleJobs
  re-deliver or contextRespawn); abortJob kills context jobs SILENTLY
  (nothing was promised in the lesson); turn-service trigger seam
- adapter: data-graph-context flattens to the canonical block (malformed
  parts have no model face)
- UI: the budget slider (home dock + /chat/new draft, the session-data
  strip); the quiet SystemLine "~537 · 10 propositions"; dock kind
  "Knowledge context"; model-picker PUT now spreads settings (a model
  pick can no longer clear the sibling override)

Live-smoked end to end on the real embedder + real GLM: seeded ledger
(10 propositions), session on "modal logic: possible worlds and the
necessity box" — job in the dock, queued behind the prober's question,
delivered on the answer, SystemLine in the transcript, wake turn reads
the block and continues the probe. Gates: tsc, lint, 459/459, build.

tests/render-activity-dock.test.tsx

@@ -152,6 +152,18 @@ describe("activity section render", () => {
 		assert.match(html, /activity-total-cost[^>]*>—</);
 	});
 
+	it("renders a graph-context job as 'Knowledge context' — the dock's fourth kind", () => {
+		const html = renderToStaticMarkup(
+			<ActivitySection
+				feed={{ jobs: [job({ id: "jctx", kind: "graph-context", activity: "selecting propositions", title: "Water cycle" })], extractions: [] }}
+			/>,
+		);
+		assert.match(html, /data-testid="activity-blob-job"/);
+		assert.match(html, /Knowledge context/);
+		assert.match(html, /selecting propositions/);
+		assert.match(html, /data-testid="activity-abort"/, "END kills the injection like any job");
+	});
+
 	it("shows total running cost when jobs are priced", () => {
 		const usage = {
 			model: "z-ai/glm-5.3-flash",