Report the highest-band link and MLO state in network band and status

[SDCVO]

Problem

On a Wi-Fi 7 MLO (Multi-Link Operation) connection, the AP exposes one radio link per band under a single SSID, and iw dev <dev> link prints each link with its own freq: line — Link 0 (typically 2.4 GHz) first:

Link 0 BSSID … 
    freq: 2412.0
Link 1 BSSID …
    freq: 5745.0
MLD … stats:
    tx bitrate: 1200.9 MBit/s 80MHz EHT-MCS 11 …

omarchy-network-band and omarchy-network-status extracted the first freq: line, so a 2.4+5 GHz association was always reported as 2.4GHZ in the network panel, even though the 5 GHz link carries the traffic and is the BSSID NetworkManager reports as in-use. Pinning the band "worked" only because it forced a single-band association.

Fix

• bin/omarchy-network-band / bin/omarchy-network-status — select the highest-band link's frequency instead of the first. Non-MLO output is unchanged (a single freq: yields the same value).
• bin/omarchy-network-band — emit a new mlo\t0|1 line, detected by counting freq: links, so the shell can tell split-link associations apart.
• shell/plugins/panels/network/Model.js — parseBandStatus reads the flag; bandSectionTitle appends · MLO beside the live band.
• shell/plugins/panels/network/Panel.qml — new bandMlo property wired into the band header.

The panel's band header now reads:

WI-FI BAND: 5GHZ · MLO

and stays plain (WI-FI BAND: 5GHZ, WI-FI BAND: 2.4GHZ) for single-link connections.

Tests

• New test/shell.d/network-band-test.sh (stubbed iw/nmcli):
  • MLO 2.4+5 → band 5, mlo 1
  • MLO 5+6 → band 6, mlo 1
  • single 5 GHz / 2.4 GHz links → unchanged bands, mlo 0
• test/shell.d/network-test.sh — coverage for the MLO header variants (live, plain, pinned) and the mlo field in parseBandStatus.
• ./test/all passes apart from the 3 pre-existing omarchy-pkgs checkout failures on this machine (environment-related, unrelated to this change).

The · MLO suffix intentionally only appears under Automatic (when the header carries the live band); once a band is pinned the pills show instead and the header stays plain — matching the existing design.