Implement per-channel remote processing (Remote: All / Selected… / None + chooser)

[Copilot]

Replaces the binary "Show Remote" toggle with a three-mode selector (All / Selected… / None) and a per-channel chooser popup. In Selected mode, only channels enabled in the uint8_t bitmask are ingested — non-selected channels are never stored, never rendered, and do not contribute to RMS or cancellation computations.

New component — RemoteChannelChooser

• RemoteChannelChooserComponent: 8 rows (Ch 1–8), each with a toggle, colour swatch, and remote label pulled from RemoteInstanceInfo (most-recently-seen instance wins per channel index).
• "All" / "None" quick-toggle buttons.
• onMaskChanged callback fires on every change; updateRemoteInfos() refreshes label/colour display.

ScopeDisplay

• Added clearRemoteChannelsNotInMask(uint8_t enabledMask) — deactivates remote slots whose bit is not set, with safe range guard on the shift.

PluginEditor — UI + logic

• Replaced remoteDisplayToggle with remoteModeLabel + remoteModeCombo + remoteChooseButton (enabled only in Selected mode).
• timerCallback() now branches on RemoteMode:
  • None → setReceiveEnabled(false), clear on transition.
  • All → ingest everything as before.
  • Selected → receive enabled, but packets/infos filtered by mask before writeRemotePackets(); calls clearRemoteChannelsNotInMask() on mask change.
• Selecting Selected… in the combo auto-opens the CallOutBox chooser; Choose… button reopens it.

// timerCallback — Selected mode filtering (deduped via lambda)
const auto isChannelEnabled = [this](int instanceIndex) -> bool {
    const int ch = instanceIndex - 1;
    return ch >= 0 && ch < 8 && (((m_remoteChannelMask) >> static_cast<unsigned>(ch)) & 1u);
};

PluginProcessor — state persistence

• Added m_remoteMode (atomic int, 0/1/2) and m_remoteChannelMask (atomic uint8_t) with getters/setters.
• Both persisted in getStateInformation / setStateInformation so mode and mask survive DAW session save/reload.