fix: upgrade Motion to address sticky session tab dragging

[turingcat]

Problem and change

Related issue: #769.

Clicking a top session tab can intermittently leave the tab in a sticky dragging state. Upgrade Motion from ^12.34.0 to ^13.4.0 and update pnpm-lock.yaml. Initial manual testing of the rebuilt macOS arm64 app has not reproduced the issue.

This crosses a major version boundary. The root cause has not been conclusively isolated, and the manual result should not be taken as proof that all drag interactions are fixed. No application behavior code is changed.

Validation

• Next.js static export completed with next build --webpack.
• Tauri release build for aarch64-apple-darwin completed; app and companion binaries were verified as arm64.
• Reporter is manually testing the rebuilt macOS app and has reported no problems so far.
• No additional automated regression run was performed for this submission, at the reporter's request.