extraction cleanup: events ledger dies, markdown source view, auditor-as-linker (2026-09-27 rulings)

The graph becomes raw reasoning chains only. Quiz outcomes and
understanding observations are no longer formalized; assessment
moves to the future practice module.

Events ledger removed end-to-end: LedgerEvent/LedgerEventKind/
UnderstandingLevel/ExtractionAttribution/AuditResult.dropped and
snapshot nodeObservations deleted from contracts; quizEvent builder
and the events step of mergeFindings gone; appendEvent/readEvents
dropped from the port and store; LEDGER_FILES loses events.jsonl
with a one-time purge of a stale file next to the nodes ledger;
graph-deletion and the delete dialog lose event purge + quiz-answer
impact counts; GraphSessionProposition becomes a pure birth list.

Whole-session markdown source view: new core/session-markdown.ts is
the shared formatting engine (id-anchored speaker blocks, quiz/
recall/question blocks, tool one-liners) — the extractor's prompt
view and the future user-facing export render from one engine.
Coverage fingerprints deliberately stay on the old line format
(content-hash semantics; re-formatting never re-opens covered
history). The whole session goes to the extractor — no phase cut.

Auditor refocused as the identity linker: never sees the source;
explores the graph via new auditor-specific tools in
agent/tools/graph.ts (find — glob over name/statement/aliases;
list_sessions; list_propositions with full statement text; no
timestamps) instead of an injected full-graph dump; equivalence
bias — paraphrases merge, only genuinely distinct propositions stay
apart; no drop channel, the extractor is fully trusted; may draw
bridging edges (typed follows/supports) between existing nodes and
the batch, resolved by the merger with chat-scoped message-less
provenance. Agentic loop, maxTurns 16.

UI: the node detail card gains an edges section above the sessions
list (follows-from / supported-by / what-follows / what-it-supports,
rendered only when present, click-to-select neighbors); the
understanding-note chips are gone.

Prober list_propositions reworded to what a session covered —
names only, no levels. docs/architecture.md + README updated to
the as-built pipeline. Gates: typecheck, 1059/1059, lint, build.

src/core/session-markdown.ts

@@ -0,0 +1,126 @@
+/**
+ * Session → markdown — the ONE formatting engine (owner ruling 2026-09-27).
+ *
+ * The extractor's view of a teaching session and the future user-facing
+ * session export share this engine: a session is rendered as clean,
+ * readable markdown — speaker headers, quiz/check-in blocks, tool notes —
+ * with the message-id anchors preserved (extraction provenance depends on
+ * the extractor reporting the `[id]` tags it saw; `anchors: false` mints
+ * the same document without them, for the user export).
+ *
+ * Pure core: native messages in (LhMessage), string out. Content parity
+ * with the coverage line builder (core/coverage.ts messageViewLines) is
+ * deliberate — every message that produces view lines produces a markdown
+ * block, in the same order — but the formats are SEPARATE by design
+ * (2026-09-27): coverage fingerprints hash the line format and stay stable
+ * (no mass re-extraction when presentation changes); markdown is
+ * presentation. A failed tool call renders nothing (retry context, not
+ * learning evidence); custom markers are invisible, same as the view.
+ */
+
+import type { LhMessage } from "./native-messages.ts";
+import type { ToolResultMessage } from "@earendil-works/pi-ai";
+
+/** The user-facing text blocks of a native message (string or text parts). */
+function textOf(content: unknown): string[] {
+	if (typeof content === "string") return content.trim() ? [content] : [];
+	if (!Array.isArray(content)) return [];
+	return content
+		.filter((c): c is { type: "text"; text: string } => (c as { type?: string }).type === "text")
+		.map((c) => c.text)
+		.filter((t) => t.trim().length > 0);
+}
+
+/** One tool result's learner-visible outcome, rendered as body lines. */
+function toolResultBody(result: ToolResultMessage): { heading: string; body: string[] } {
+	const out = result.details as
+		| Partial<{
+				questionText: string;
+				correct: boolean;
+				dontKnow: boolean;
+				note: string;
+				text: string;
+				answers: string[];
+				other: string;
+				dismissed: boolean;
+		  }>
+		| undefined;
+
+	if (result.toolName === "quiz" || result.toolName === "explain") {
+		const heading = result.toolName === "quiz" ? "Quiz" : "Recall check";
+		const question = typeof out?.questionText === "string" && out.questionText ? out.questionText : "(no question text)";
+		const body = [`**Q:** ${question}`];
+		if (out?.dismissed === true) body.push("The learner skipped this check.");
+		else if (out?.dontKnow === true) body.push("The learner did not know.");
+		else if (out?.correct === true) body.push("The learner answered correctly.");
+		else if (out?.correct === false) body.push("The learner answered incorrectly.");
+		else if (typeof out?.text === "string" && out.text.trim()) body.push(`The learner answered in his own words: ${out.text.trim()}`);
+		if (typeof out?.note === "string" && out.note) body.push(`*(his thinking: ${out.note})*`);
+		return { heading, body };
+	}
+
+	if (result.toolName === "ask_user_question") {
+		const question = typeof out?.questionText === "string" && out.questionText ? out.questionText : "(no question text)";
+		const body = [`**Q:** ${question}`];
+		const chosen = [
+			...(Array.isArray(out?.answers) ? out!.answers! : []),
+			...(typeof out?.other === "string" && out.other.trim() ? [out.other.trim()] : []),
+		];
+		if (typeof out?.text === "string" && out.text.trim()) body.push(`The learner answered: ${out.text.trim()}`);
+		else if (chosen.length > 0) body.push(`The learner chose: ${chosen.join(", ")}`);
+		else if (out?.dismissed === true) body.push("The learner skipped this question.");
+		if (typeof out?.note === "string" && out.note) body.push(`*(his thinking: ${out.note})*`);
+		return { heading: "Question", body };
+	}
+
+	// Parity with the line builder: other clean tool results are one line.
+	return { heading: "Tool", body: [`*${result.toolName} result delivered*`] };
+}
+
+/**
+ * ONE message as a markdown block — `null` when the message renders
+ * nothing (a failed tool call, a bare marker, an empty text part set).
+ * `mid` is the provenance anchor shown when `anchors` is on.
+ */
+export function messageMarkdown(message: LhMessage, mid: string, anchors = true): string | null {
+	const role = (message as { role?: string }).role;
+	const anchor = anchors ? ` · ${mid}` : "";
+	const parts: string[] = [];
+
+	if (role === "user") {
+		for (const text of textOf((message as { content: unknown }).content)) {
+			parts.push(`### Learner${anchor}\n\n${text.trim()}`);
+		}
+	} else if (role === "assistant") {
+		for (const text of textOf((message as { content: unknown }).content)) {
+			parts.push(`### Teacher${anchor}\n\n${text.trim()}`);
+		}
+	} else if (role === "toolResult") {
+		const result = message as ToolResultMessage;
+		if (result.isError) return null; // retry context, not learning evidence
+		const { heading, body } = toolResultBody(result);
+		parts.push(`### ${heading}${anchor}\n\n${body.join("\n\n")}`);
+	}
+
+	// custom markers are invisible, same as the extraction view.
+	return parts.length > 0 ? parts.join("\n\n") : null;
+}
+
+/**
+ * A whole session (or one extraction BATCH — same engine, subset of
+ * messages) as one markdown document. Blocks render in message order;
+ * messages that render nothing are skipped silently. The optional title
+ * mints the document header (`# <title>`).
+ */
+export function sessionMarkdown(
+	messages: ReadonlyArray<LhMessage>,
+	opts: { title?: string; anchors?: boolean } = {},
+): string {
+	const blocks: string[] = [];
+	if (opts.title !== undefined && opts.title.length > 0) blocks.push(`# ${opts.title}`);
+	for (const message of messages) {
+		const block = messageMarkdown(message, (message as { id?: string }).id ?? "", opts.anchors ?? true);
+		if (block !== null) blocks.push(block);
+	}
+	return blocks.join("\n\n");
+}