[Desktop] Add screen-reader smoke coverage

[TheZupZup]

Part of #376.

Goal

Create a small repeatable Linux screen-reader smoke checklist/test for the desktop build.

Likely code areas

• accessibility/semantics tests
• docs/manual-test-checklist.md or Linux desktop docs
• shared desktop/player/library widgets if smoke finds gaps

Requirements

• Cover app identity, sidebar navigation, representative track/album rows, Now Playing controls, sliders, dialogs and connection management.
• Verify names, states and actions are announced meaningfully rather than only checking that a Semantics node exists.
• Include keyboard-only traversal as part of the smoke.
• Keep the checklist reproducible with a commonly available Linux screen reader; note desktop-specific limitations.

Acceptance criteria

• Repeatable screen-reader checklist exists.
• Core playback/navigation can be operated and understood without sight.
• Major unlabeled controls discovered by the smoke are fixed or filed separately.
• No private server/token information is announced unexpectedly.
• Automated semantics coverage complements the manual smoke where practical.