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.

src/server/pi/record-adapter.ts

@@ -1,7 +1,8 @@
 import type { UIMessage } from "ai";
 import type { AgentMessage } from "@earendil-works/pi-agent-core";
 import type { AssistantMessage, Message, ToolResultMessage } from "@earendil-works/pi-ai";
-import { HANDOFF_TEXT, verdictText } from "../../core/contracts/chat.ts";
+import { graphContextOfMessage } from "../../core/graph-context.ts";
+import { graphContextText, HANDOFF_TEXT, verdictText } from "../../core/contracts/chat.ts";
 
 /**
  * The record → pi-ai transcript adapter (docs/pi-engine-swap.md §4). The
@@ -55,12 +56,19 @@ function zeroUsage() {
 
 /** The model-facing text of a marker-only user message, or null when the
  *  message has no model face at all (UI-only data parts). */
-function systemTextOf(parts: ReadonlyArray<{ type: string; data?: unknown }>): string | null {
-	for (const part of parts) {
+function systemTextOf(message: { parts: ReadonlyArray<{ type: string; data?: unknown }> }): string | null {
+	for (const part of message.parts) {
 		if (part.type === "data-verdict") {
 			return verdictText((part.data as { accepted?: unknown } | undefined)?.accepted === true);
 		}
 		if (part.type === "data-probe-handoff") return HANDOFF_TEXT;
+		// Graph context injection: the block text derives from the part's
+		// validated data (parse-don't-cast — a malformed part has no model
+		// face, and the message then never reaches the provider).
+		if (part.type === "data-graph-context") {
+			const data = graphContextOfMessage({ parts: message.parts });
+			return data ? graphContextText(data) : null;
+		}
 	}
 	return null;
 }
@@ -79,7 +87,7 @@ export function recordToPiMessages(messages: UIMessage[]): Message[] {
 			// wording lives in the adapter's reach (core contracts), never
 			// authored as fake human speech in the transcript.
 			if (texts.length === 0) {
-				const flat = systemTextOf(message.parts);
+				const flat = systemTextOf(message);
 				if (flat === null) continue; // pure UI data part, no model face
 				texts.push(flat);
 			}