revert(status-line): restored single-row status bar with priority drop

- Reverted PR #5751 (issue #5749): continuation rows wrapped the editor
  top border onto extra lines, which is unacceptable for the input frame.
- EditorTopBorder is back to a single content/width pair; narrow widths
  drop right segments, shrink the path, then drop left segments.

packages/coding-agent/src/modes/controllers/selector-controller.ts

@@ -201,10 +201,7 @@ export class SelectorController {
 					getStatusLinePreview: () => {
 						// Return the rendered status line for inline preview
 						const availableWidth = this.ctx.editor.getTopBorderAvailableWidth(this.ctx.ui.terminal.columns);
-						return this.ctx.statusLine
-							.getTopBorder(availableWidth)
-							.lines.map(line => line.content)
-							.join("\n");
+						return this.ctx.statusLine.getTopBorder(availableWidth).content;
 					},
 					onPluginsChanged: async () => {
 						const projectPath = await resolveActiveProjectRegistryPath(this.ctx.sessionManager.getCwd());