fix(linux): repair unresponsive UI on startup and full-screen panels

Linux users reported the window UI (including native title bar buttons)
couldn't receive clicks until manually maximizing and restoring the
window. Root causes: (1) Tauri webview did not acquire focus on startup
so first clicks were consumed by X11/Wayland click-to-activate
(Tauri #10746, wry #637); (2) GTK surface input region failed to
renegotiate on the visible:false + show() path under some
WebKitGTK/compositor combinations.

- Add linux_fix::nudge_main_window helper that performs set_focus plus
  a ±1px no-op resize after window show, with a 500ms reconciliation
  readback to compensate for dropped resize requests on slow
  compositors.
- Wire the helper into every window re-show path: normal startup,
  deeplink, single_instance, tray show_main, and lightweight exit.
- Set WEBKIT_DISABLE_COMPOSITING_MODE=1 at startup to avoid resize
  crashes and Wayland surface negotiation issues.
- Remove data-tauri-drag-region on Linux from App.tsx header and the
  shared FullScreenPanel (used by all provider/MCP/workspace forms)
  to avoid Tauri #13440 in Wayland sessions. Extract drag-region
  constants to src/lib/platform.ts for reuse.

All Rust changes are gated by #[cfg(target_os = "linux")]; frontend
changes preserve macOS/Windows behavior via runtime isLinux() checks.
Known limitation: tiling Wayland compositors ignore set_size, so
GDK_BACKEND=x11 remains the user-side workaround.

src-tauri/src/lib.rs

@@ -13,6 +13,8 @@ mod gemini_config;
 mod gemini_mcp;
 mod init_status;
 mod lightweight;
+#[cfg(target_os = "linux")]
+mod linux_fix;
 mod mcp;
 mod openclaw_config;
 mod opencode_config;
@@ -132,6 +134,10 @@ fn handle_deeplink_url(
                     let _ = window.unminimize();
                     let _ = window.show();
                     let _ = window.set_focus();
+                    #[cfg(target_os = "linux")]
+                    {
+                        linux_fix::nudge_main_window(window.clone());
+                    }
                     log::info!("✓ Window shown and focused");
                 }
             }
@@ -229,6 +235,10 @@ pub fn run() {
                 let _ = window.unminimize();
                 let _ = window.show();
                 let _ = window.set_focus();
+                #[cfg(target_os = "linux")]
+                {
+                    linux_fix::nudge_main_window(window.clone());
+                }
             }
         }));
     }
@@ -899,6 +909,14 @@ pub fn run() {
                     // 正常启动模式：显示窗口
                     let _ = window.show();
                     log::info!("正常启动模式：主窗口已显示");
+
+                    // Linux: 解决首次启动 UI 无响应问题（Tauri #10746 + wry #637）。
+                    // 启动时 webview 未获取焦点 + surface 尺寸协商失败，导致点击无效。
+                    // 这里做 set_focus + 伪 resize，等价于无视觉版本的"最大化-还原"。
+                    #[cfg(target_os = "linux")]
+                    {
+                        linux_fix::nudge_main_window(window.clone());
+                    }
                 }
             }