layered Esc: an open overlay claims Esc before the abort chain (owner 2026-10-04)

Esc over a mermaid focus, the plan popup, or the setup dialog opened the
question-dismiss confirm underneath — KeyboardShortcuts' window listener
registers first, so the overlays' own self-closing Esc listeners could
never outrun the lh:kbd-abort-turn dispatch. The state gate in ChatView
is the defense (the architecture's own pattern from the abort dialog):
escAbortTarget, exported pure, rules priority by stacking order — abort
confirm (claimed by its dialog) > mermaid (paints above plan) > plan >
setup (self-closing) > question > turn. The gate closes the overlay; the
overlays' own listeners stay (idempotent). Pinned in esc-layering.test.

tests/esc-layering.test.ts

@@ -0,0 +1,46 @@
+import assert from "node:assert/strict";
+import { describe, it } from "node:test";
+import { escAbortTarget } from "../components/chat.tsx";
+
+/**
+ * THE LAYERED ESC (owner report, 2026-10-04): Esc over an open overlay —
+ * a mermaid focus, the plan popup, the setup dialog — must CLOSE THE
+ * OVERLAY, never dismiss a pending question (or abort a turn) underneath.
+ * KeyboardShortcuts dispatches lh:kbd-abort-turn on every unclaimed Esc
+ * and its window listener registers FIRST, so the overlays' own listeners
+ * can never outrun it — the state gate in ChatView (this ruling, exported
+ * 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 };
+
+	it("no overlays: the 2026-10-02 chain stands (question before turn)", () => {
+		assert.equal(escAbortTarget({ ...none, pending: true }), "question");
+		assert.equal(escAbortTarget({ ...none, busy: true }), "turn");
+		assert.equal(escAbortTarget(none), null);
+		assert.equal(escAbortTarget({ ...none, pending: true, busy: true }), "question", "a pending question outranks the turn");
+	});
+
+	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 });
+			assert.notEqual(target, "question", `${overlay} open must not dismiss the question`);
+			assert.notEqual(target, "turn", `${overlay} open must not abort the turn`);
+		}
+		assert.equal(escAbortTarget({ ...none, mermaidFocus: true, pending: true }), "mermaid");
+		assert.equal(escAbortTarget({ ...none, planOpen: true, pending: true }), "plan");
+		assert.equal(escAbortTarget({ ...none, setupOpen: true, pending: true }), "setup");
+	});
+
+	it("the abort confirm is topmost — its own Esc is claimed by the dialog", () => {
+		assert.equal(
+			escAbortTarget({ ...none, abortAsk: true, mermaidFocus: true, pending: true }),
+			null,
+			"never chain: the dialog owns that Esc",
+		);
+	});
+
+	it("stacking order among overlays: mermaid paints above plan (later in DOM)", () => {
+		assert.equal(escAbortTarget({ ...none, mermaidFocus: true, planOpen: true, pending: true }), "mermaid");
+	});
+});