fix(tui): restore ask focus after settings

[roboomp]

Repro

Opening /settings while a model turn is still running can leave an ask selector pending underneath the fullscreen settings overlay. The minimal focus repro is: focus the prompt editor, open a fullscreen settings overlay, attempt to focus a pending ask selector while the overlay is visible, close the overlay, and assert the ask selector has focus; before the fix it prints duringOverlay=settings and afterClose=editor and exits 1.

Cause

SelectorController.showSettingsSelector in packages/coding-agent/src/modes/controllers/selector-controller.ts always called ui.setFocus(this.ctx.editor) when the settings overlay closed. If ExtensionUiController.showHookSelector had already mounted an ask selector in editorContainer, the fullscreen overlay prevented that selector from taking focus until close, and the settings close handler then forced focus back to the main prompt editor.

Fix

• Added getEditorSurfaceFocusTarget to choose the active hook selector/input/editor before falling back to the main prompt editor.
• Updated the /settings close path to restore focus to that active editor-surface component after hiding the overlay.
• Added a regression test covering the fullscreen overlay close sequence with a pending ask selector.
• Added a coding-agent changelog entry for Can't answer ask tool after exiting /settings #3203.

Verification

Ran bun test test/settings-focus.test.ts and bun run check:types in packages/coding-agent; both passed. gh_push_branch completed the pre-publish gate and pushed the branch. Fixes #3203