practice UI: the dock, the transcript cards, layered-Esc discard

- PracticeDock (components/practice-dock.tsx): the active problem
  replaces the composer — statement (markdown+LaTeX) above, the 'Your
  thinking' composer-twin below with the two submit lanes (Nudge =
  thinking without a commit; Commit = answer commit; ⌘/Ctrl+Enter
  commits). Dictation claims the thinking field.
- Transcript cards (practice-cards.tsx + the artifact registry): the
  problem card (compact-expandable statement — the commitment NEVER
  renders), the conclude card (outcome + verdict + reveal; the
  dismissal synthesis is one muted line), and the user-side thinking
  register cards (Your thinking / Your solution).
- view.ts: the problem pose joins the placeholder fork (the ack never
  flips the part); practice-thinking markers project as data parts;
  problem-dismissed markers project nothing.
- chat.tsx: activeProblemOf drives the dock branch (question > problem
  > composer), the esc layering gains the problem rung (below question,
  above turn) with its discard confirm + the silent marker route; the
  thinking submissions POST through the session's optimistic appends.

tests/esc-layering.test.ts

@@ -12,7 +12,7 @@ import { escAbortTarget } from "../components/chat.tsx";
  * pure) is the defense. Priority = stacking order.
  */
 describe("escAbortTarget (the layered-Esc ruling)", () => {
-	const none = { abortAsk: false, mermaidFocus: false, planOpen: false, setupOpen: false, pending: false, busy: false };
+	const none = { abortAsk: false, mermaidFocus: false, planOpen: false, setupOpen: false, pending: false, problem: false, busy: false };
 
 	it("no overlays: the 2026-10-02 chain stands (question before turn)", () => {
 		assert.equal(escAbortTarget({ ...none, pending: true }), "question");
@@ -21,6 +21,12 @@ describe("escAbortTarget (the layered-Esc ruling)", () => {
 		assert.equal(escAbortTarget({ ...none, pending: true, busy: true }), "question", "a pending question outranks the turn");
 	});
 
+	it("an active practice problem sits between question and turn (2026-10-04)", () => {
+		assert.equal(escAbortTarget({ ...none, problem: true }), "problem");
+		assert.equal(escAbortTarget({ ...none, problem: true, busy: true }), "problem", "the problem card outranks the turn abort");
+		assert.equal(escAbortTarget({ ...none, planOpen: true, problem: true }), "plan", "an open popup still outranks the problem");
+	});
+
 	it("an open overlay claims Esc over a pending question — the owner's report", () => {
 		for (const overlay of ["mermaidFocus", "planOpen", "setupOpen"] as const) {
 			const target = escAbortTarget({ ...none, [overlay]: true, pending: true });