fix(orchestrator): clamp mobile status-bar levels to root width

The mobile status-bar chrome injected by `mobile_status_bar_json`
hardcoded levels.x=286 — the right-aligned cellular/wifi/battery
group, sized for a 390-wide iPhone reference. When the C2 plan
work started honouring explicit prompt sizes via
`explicit_mobile_size` (accepts 240..=520 wide), a 320 x 568
iPhone-SE prompt rendered the chrome at x=286..364 — 44 px past
the right edge.

Take root `width` as an argument and derive levels.x as
`width - 78 - 26` (78 = chrome width, 26 = iOS safe-area gutter,
matches the existing 390 reference: 390 - 104 = 286). New test
exercises 320-wide root to lock in the no-overflow contract.

crates/op-orchestrator/src/scaffold.rs

@@ -84,7 +84,15 @@ fn status_bar_foreground(fill_hex: &str) -> &'static str {
     }
 }
 
-fn mobile_status_bar_json(root_id: &str, fill_hex: &str) -> serde_json::Value {
+/// Status-bar chrome for a mobile root frame. `width` is the root frame's
+/// width so the right-aligned levels group (cellular/wifi/battery) clamps
+/// to the screen edge instead of overflowing on explicit narrow widths
+/// (e.g. 320 × 568 iPhone SE). Right-edge inset = 26 to match the iOS
+/// safe-area gutter the 390-wide reference is built against.
+fn mobile_status_bar_json(root_id: &str, fill_hex: &str, width: f64) -> serde_json::Value {
+    const LEVELS_WIDTH: f64 = 78.0;
+    const LEVELS_RIGHT_INSET: f64 = 26.0;
+    let levels_x = (width - LEVELS_WIDTH - LEVELS_RIGHT_INSET).max(0.0);
     let fg = status_bar_foreground(fill_hex);
     let fg_fill = solid_fill_json(fg);
     let time_label = serde_json::json!({
@@ -186,9 +194,9 @@ fn mobile_status_bar_json(root_id: &str, fill_hex: &str) -> serde_json::Value {
         "type": "frame",
         "id": format!("{root_id}-status-bar-levels"),
         "name": "Levels",
-        "x": 286,
+        "x": levels_x,
         "y": 24,
-        "width": 78,
+        "width": LEVELS_WIDTH,
         "height": 14,
         "layout": "none",
         "children": [cellular, wifi, battery]
@@ -224,7 +232,7 @@ fn build_root_frame_node(
     is_mobile: bool,
 ) -> Result<PenNode, String> {
     let children = if is_mobile {
-        serde_json::json!([mobile_status_bar_json(id, fill_hex)])
+        serde_json::json!([mobile_status_bar_json(id, fill_hex, width)])
     } else {
         serde_json::json!([])
     };

crates/op-orchestrator/src/scaffold_tests.rs

@@ -116,6 +116,31 @@ fn build_scaffold_mobile_status_bar_uses_fixed_icon_positions() {
     }
 }
 
+#[test]
+fn build_scaffold_mobile_status_bar_clamps_levels_to_explicit_narrow_width() {
+    // iPhone SE: 320 wide. The pre-fix scaffold hardcoded levels.x=286
+    // which put the right-aligned chrome (cellular/wifi/battery, 78 wide)
+    // at x=286..364 — 44 px off-screen on a 320-wide root.
+    let mut narrow = plan();
+    narrow.root_frame.width = 320.0;
+    let cmds = build_scaffold(&narrow, true).expect("scaffold");
+    match &cmds[0] {
+        EditorCommand::InsertSubtree { nodes, .. } => {
+            let status_json = serde_json::to_value(&nodes[0].children().expect("children")[0])
+                .expect("status json");
+            let levels = &status_json["children"][1];
+            let levels_x = levels["x"].as_f64().expect("levels x");
+            let levels_w = levels["width"].as_f64().expect("levels width");
+            assert!(
+                levels_x + levels_w <= 320.0,
+                "levels right edge {} overflows root width 320",
+                levels_x + levels_w
+            );
+        }
+        other => panic!("expected InsertSubtree, got {other:?}"),
+    }
+}
+
 #[test]
 fn build_scaffold_single_root_uses_safe_canvas_offset() {
     let cmds = build_scaffold(&plan(), true).expect("scaffold");