feat(harness): bind Escape key to cancel in-progress turn when canvas is focused

docs/harness-limits.md

@@ -48,6 +48,7 @@ click/tap scrolls the transcript so the message is back in view near the top.
 | **Enter** (composer focused) | Insert a newline (composer is multi-line) |
 | **Ctrl+Enter** / **Cmd+Enter** (composer focused) | Send prompt when idle; **enqueue** a follow-up when Busy |
 | **↑** / **↓** (composer focused) | **↑** on an empty composer loads the newest user message; further ↑ walk older user rows. **↓** walks forward; ↓ past the newest restores the in-progress draft. Only user messages appear (assistant/thinking/tool/system/error/skill rows never load). Works while Busy. Ring window only (Load earlier for prompts that have aged out) |
+| **Escape** (harness focused, Busy) | Cancel the in-progress turn (same as ■ Stop). Queue-row editor: dismisses editor first (does not abort turn). Idle: no-op |
 | Tab | DOM nav / Clear (canvas uses pointer + dvui focus) |
 | Composer focus | Requested on ready and after each send |
 

native/harness/src/ui.zig

@@ -634,6 +634,19 @@ pub fn frame() !void {
                     continue;
                 }
 
+                // ── Escape — cancel in-progress turn (plan #705) ─────────────
+                // Same path as the ■ Stop icon. Only .down fires cancel (single-
+                // fire). Gated on busy so idle Esc is not marked handled and can
+                // still close dvui menus (MenuWidget.processEventsAfter). Skip
+                // when a queue-row editor is open — queue_band owns Esc there.
+                if (busy and ke.code == .escape and ke.action == .down and
+                    state.queue_editing_index == null)
+                {
+                    e.handled = true;
+                    bridge.queueCancelFromUi();
+                    continue;
+                }
+
                 // ── Composer arrow-key history (plan #667) ───────────────────
                 // ↑ enters history when the composer is empty OR while already
                 // in history. ↓ walks history forward; outside history ↓ passes