practice round: dead session starts, prompt laws, preamble, label unify

THE START BUG (owner report, reproduced live both kinds): new sessions
(?prompt flow — practice and teach alike) sat dead until a second
message, which then persisted WITHOUT the first. Root cause, proven
both directions: the submit POST rode the view's consumeAbort
controller; React StrictMode's simulated remount fires Diet A's
unmount cleanup (model.stop()) ~8ms in and killed the POST mid-flight;
the page's sentInitial guard had already flipped, so it never retried.
Teach was equally broken — only unnoticed, because every teach chat in
use predates the diet and practice starts are always fresh. Fix: the
submit law — POSTs are not abortable by view teardown (they are ~100ms
acks since Diet B and cannot starve the pool); after the ack, a
consumeAbort identity check guards the stream attach. Pinned with the
stop-mid-submit regression test. Live: StrictMode on, practice draft
POST 200/67ms, stream attached, message persisted, problem posed.

PRACTICE PROMPT (00-base): the opening rule — material arrives two
ways, both first-class (picked propositions primary; free-form —
topics, course material, files/PDFs — fully supported, never refused);
as soon as material exists the reply poses, at most one short line
before the problem call, no warm-up interview. Plus the hard law: no
problem is ever conversation — every problem through the tool (no
thinking field/no reveal/no verdict attaches to prose).

GRAPH-CONTEXT PREAMBLE: custom markers flatten to user-role on the
wire, so the old "Contextualization — the learner picked…" read like a
system broadcast in the learner's voice channel. Now the bracket
convention: "[Session context] — picked from the learner's knowledge
map…".

SIDEBAR: busy rows unify to "Working…" for both kinds (the spinner's
default label included); "Practicing…"/"Teacher is working…" retired.

Gates: 1490/1490, typecheck, lint. doctrine's stale doc pointer fixed.

tests/render-sidebar.test.tsx

@@ -67,7 +67,7 @@ describe("SessionRow", () => {
 		assert.ok(html.includes("braille-frame"), "CSS-animated frames");
 		assert.ok((html.match(/class="braille-frame"/g) ?? []).length === 10, "all ten frames");
 		assert.ok(html.includes('data-frame="0"'), "frame 0 leads (static fallback)");
-		assert.ok(html.includes("Teacher is working"), "accessible label");
+		assert.ok(html.includes("Working"), "accessible label");
 		assert.ok(!html.includes("bg-attention"), "no colored state fill — monochrome by design");
 	});
 
@@ -77,7 +77,7 @@ describe("SessionRow", () => {
 		// contract can't silently re-widen: an extraction-only "working"
 		// row would be a double signal.
 		const html = render(item({ busy: true, pendingQuestion: false }));
-		assert.ok(html.includes("Teacher is working"), "the spinner's label names the turn, not agents");
+		assert.ok(html.includes("Working"), "the spinner's label names the turn, not agents");
 	});
 
 	it("the meta line: state replaces the count when the state is the useful fact", () => {
@@ -87,7 +87,7 @@ describe("SessionRow", () => {
 		assert.ok(!awaiting.includes("braille-spinner"), "…and the spinner stays off");
 
 		const working = render(item({ busy: true }));
-		assert.ok(working.includes("Teacher is working…"), "working meta");
+		assert.ok(working.includes("Working…"), "working meta");
 
 		// Owner, typography round 5: the message count is dropped — it
 		// informed no decision. Idle meta is just how long ago.
@@ -121,9 +121,10 @@ describe("timeAgo", () => {
 });
 
 describe("SessionRow practice badge (practice sessions, 2026-10-04)", () => {
-	it("a practice row carries the dumbbell badge and the Practicing meta while busy", () => {
+	it("a practice row carries the dumbbell badge and the unified Working meta while busy (owner, 2026-10-10)", () => {
 		const html = render(item({ kind: "practice", busy: true }));
-		assert.match(html, /Practicing…/);
+		assert.match(html, /Working…/);
+		assert.doesNotMatch(html, /Practicing…/);
 		assert.match(html, /aria-label="Practice session"/);
 	});
 
@@ -133,9 +134,9 @@ describe("SessionRow practice badge (practice sessions, 2026-10-04)", () => {
 		assert.doesNotMatch(html, /Practicing…/);
 	});
 
-	it("busy teaching rows still say the teacher is working", () => {
+	it("busy teaching rows say the same unified Working", () => {
 		const html = render(item({ busy: true }));
-		assert.match(html, /Teacher is working…/);
+		assert.match(html, /Working…/);
 	});
 
 	it("a practice row with a posed problem says the problem is waiting", () => {