session kind: ChatRecord.kind teach|practice (absent = teach)

Practice sessions (owner, 2026-10-04): the marker rides the record and
the normalized summary (absent field reads as teach — pre-practice
records never migrate); POST /api/chats accepts {kind: 'practice'}.
The agent branch, tools, and UI land in the following slices.

tests/chat-kind.test.ts

@@ -0,0 +1,46 @@
+/**
+ * SESSION-KIND PINS (practice sessions, owner 2026-10-04): ChatRecord.kind
+ * is ABSENT-BY-DEFAULT — absence reads as teach, so pre-practice records
+ * never migrate; "practice" marks an adaptive-practice session (the
+ * practice agent + its two tools from turn 1, no extraction, no graph
+ * writes). The store normalizes at the summary projection; createChat
+ * stamps the marker only for practice. Runs under an isolated LH_DATA_DIR
+ * (the chat-birth-stamp discipline: the seam is set before any
+ * config-loading import, so every app-module import is dynamic).
+ */
+
+import assert from "node:assert/strict";
+import fs from "node:fs";
+import * as os from "node:os";
+import * as path from "node:path";
+import { after, describe, it } from "node:test";
+
+// ── the seam, BEFORE any config-loading import ──────────────────────────────
+const TMP_DATA = fs.mkdtempSync(path.join(os.tmpdir(), "lh-chat-kind-"));
+process.env.LH_DATA_DIR = TMP_DATA;
+
+const { chatStore } = await import("../src/store/chats.ts");
+
+after(() => {
+	fs.rmSync(TMP_DATA, { recursive: true, force: true });
+});
+
+describe("session kind (practice sessions, 2026-10-04)", () => {
+	it("createChat default carries NO kind field — absence reads as teach", () => {
+		const chat = chatStore.createChat("plain session");
+		assert.equal("kind" in chat, false, "teach records carry no kind marker");
+	});
+
+	it("createChat(kind: 'practice') stamps the marker on record + list", () => {
+		const chat = chatStore.createChat("practice session", "practice");
+		assert.equal(chat.kind, "practice");
+		const listed = chatStore.listChats().find((c) => c.id === chat.id);
+		assert.equal(listed?.kind, "practice");
+	});
+
+	it("the summary projection NORMALIZES: absent record field reads as teach", () => {
+		const chat = chatStore.createChat("another plain one");
+		const listed = chatStore.listChats().find((c) => c.id === chat.id);
+		assert.equal(listed?.kind, "teach");
+	});
+});

tests/render-sidebar.test.tsx

@@ -21,6 +21,7 @@ function item(overrides: Partial<ChatListItem>): ChatListItem {
 	return {
 		id: "c1",
 		title: "Test session",
+		kind: "teach",
 		createdAt: "2026-01-01T00:00:00.000Z",
 		updatedAt: "2026-01-02T00:00:00.000Z",
 		messageCount: 4,