fix(harness): remove !busy guard so arrow-key history works during inference

docs/harness-limits.md

@@ -47,7 +47,7 @@ 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, idle) | **↑** 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). Not active while Busy — arrows pass through to the text caret. Ring window only (Load earlier for prompts that have aged out) |
+| **↑** / **↓** (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) |
 | Tab | DOM nav / Clear (canvas uses pointer + dvui focus) |
 | Composer focus | Requested on ready and after each send |
 

native/harness/src/ui.zig

@@ -641,10 +641,11 @@ pub fn frame() !void {
                 // are handled so a held arrow walks instead of also moving the
                 // caret (matching shell readline).
                 //
-                // Skip history when busy (model is running — arrows pass through
-                // to textEntry) or when editing a queued item (queue-row editor
-                // owns the caret).
-                if (!busy and state.queue_editing_index == null) {
+                // When editing a queued item the queue-row editor owns the caret,
+                // so arrows pass through. History works during inference because
+                // historyApply is a pure in-memory read (no bridge write, no
+                // alloc, no I/O).
+                if (state.queue_editing_index == null) {
                     if (ke.action == .down or ke.action == .repeat) {
                         if (ke.code == .up) {
                             const in_hist = state.history_index != null;