Show the advertised PC platform

[OwenMcGirr]

Goal

Read the platform advertised by the Switchify PC Rust preview and show it on nearby PC rows.

Acceptance criteria

• Parse optional platform values windows and macos from the BLE status payload.
• Preserve discovery for legacy, missing, or unknown platform values.
• Prefix nearby PC row summaries with the known platform.
• Do not persist platform metadata or change saved offline rows.
• Keep compilation and relevant unit tests passing.

Coordination

Switchify PC producer: switchifyapp/switchify-pc#512

Merge this Android consumer first so the platform is visible as soon as the Rust preview sends it.

[OwenMcGirr]

Implemented in #2767 and merged into v3.0.0.