Collapse stereo pairs into a single leader-controlled speaker

[gaelsimon]

A HEOS stereo pair came back as two players plus a group, shown as two separate rows. This treats a pair as one leader-controlled speaker, while keeping genuine multi-room groups expanded.

How it tells them apart: the HEOS CLI gives no signal, but the AIOS GroupControl UPnP service reports each member's audio channel (LEFT/RIGHT for a stereo/surround bond, NORMAL for a plain group). After groups load we read those channels per member (best-effort, non-blocking) and expand only the confirmed all-NORMAL groups. Any failed or missing read leaves the group collapsed, so a stereo pair never regresses to two rows.

• New GroupControl UPnP client (mirrors the existing ACT client), mock-tested against LEFT/RIGHT and NORMAL responses.
• Collapsed groups show one leader row named after the group; selection and playback events target the leader. Multi-room members stay individually listed and selectable.
• Selected-speaker name in the toolbar now matches the list (group name when collapsed).

Fixes #3 and #4 (one row per pair; consistent codec/bitrate since metadata reads off the leader).

Note: validated with mocked UPnP responses built from the real device SCPD; the exact live response of an actual pair couldn't be captured (single device on hand), so the safe fallback is collapse.

Closes #3
Closes #4

[sonarqubecloud]

Quality Gate passed

Issues
7 New issues
0 Accepted issues

Measures
0 Security Hotspots
96.1% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud