fix(tui): honor documented mouse_tracking config key (#17188)

* fix(tui): honor documented mouse_tracking config key

The TUI runtime was reading display.tui_mouse while docs and user-facing
examples pointed users at display.mouse_tracking. That made persistent
mouse-disable config look like a no-op for users trying to restore native
terminal selection/copy behavior on Linux/SSH/tmux terminals.

Use display.mouse_tracking as the canonical key, keep display.tui_mouse as
a legacy fallback, and have /mouse write the documented key. Both gateway
config.get and client-side config sync now share the same precedence: the
canonical key wins, then the legacy key, then default on.

* review(copilot): align mouse tracking config coercion

- Load gateway config once before deriving display.mouse_tracking state.
- Use key-presence precedence on the TUI client too, so canonical
  mouse_tracking wins over legacy tui_mouse even when the value is null.
- Treat numeric 0 as disabled on both gateway and client, matching the
  existing string "0" handling.
- Widen ConfigDisplayConfig mouse fields because config.get full returns raw
  YAML, not normalized booleans.

ui-tui/src/app/useConfigSync.ts

@@ -63,6 +63,19 @@ export const normalizeIndicatorStyle = (raw: unknown): IndicatorStyle => {
   return INDICATOR_STYLE_SET.has(v) ? v : DEFAULT_INDICATOR_STYLE
 }
 
+const FALSEY_MOUSE = new Set(['0', 'false', 'no', 'off'])
+const hasOwn = (obj: object, key: PropertyKey) => Object.prototype.hasOwnProperty.call(obj, key)
+
+export const normalizeMouseTracking = (display: { mouse_tracking?: unknown; tui_mouse?: unknown }): boolean => {
+  const raw = hasOwn(display, 'mouse_tracking') ? display.mouse_tracking : display.tui_mouse
+
+  if (raw === false || raw === 0) {
+    return false
+  }
+
+  return typeof raw === 'string' ? !FALSEY_MOUSE.has(raw.trim().toLowerCase()) : true
+}
+
 const MTIME_POLL_MS = 5000
 
 const quietRpc = async <T extends Record<string, any> = Record<string, any>>(
@@ -88,7 +101,7 @@ export const applyDisplay = (cfg: ConfigFullResponse | null, setBell: (v: boolea
     detailsModeCommandOverride: false,
     indicatorStyle: normalizeIndicatorStyle(d.tui_status_indicator),
     inlineDiffs: d.inline_diffs !== false,
-    mouseTracking: d.tui_mouse !== false,
+    mouseTracking: normalizeMouseTracking(d),
     sections: resolveSections(d.sections),
     showCost: !!d.show_cost,
     showReasoning: !!d.show_reasoning,