Suppress Qt TextToSpeech plugin loading errors on Linux

[Copilot]

Description

Qt emits critical errors when TextToSpeech plugins fail to load (e.g., speech-dispatcher missing on Linux). These errors are harmless—AudioOutput already handles missing TTS engines gracefully—but alarm users.

Changes:

• Filter Qt TTS plugin loading errors in QGCLogging::msgHandler()
• Downgrade QtCriticalMsg from qt.speech.tts.* categories containing "Error loading text-to-speech plug-in" to QtDebugMsg
• Generic filter handles any TTS backend (speechd, flite, etc.)

// Added in QGCLogging.cc msgHandler()
if (type == QtCriticalMsg && 
    QString(context.category).startsWith("qt.speech.tts") &&
    msg.contains("Error loading text-to-speech plug-in", Qt::CaseInsensitive)) {
    type = QtDebugMsg;
}

Test Steps

1. Run QGC on Linux without speech-dispatcher installed
2. Verify no critical TTS errors appear in logs
3. Verify TTS continues working on systems where it's properly configured

Checklist:

• Review Contribution Guidelines.
• Review Code of Conduct.
• I have tested my changes.

Related Issue

Fixes issue where critical error "Error loading text-to-speech plug-in 'speechd'" appears on Linux Mint 22.1.

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Original prompt

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This section details on the original issue you should resolve

<issue_title>Text to speech does not work on Linux Mint 22.1.</issue_title>
<issue_description>### Have you checked the latest release for fixes?

• Yes, I’ve tested on the latest release

Description

Expected Behavior
Describe what you thought should happen here.

Text to speech works.

Current Behavior
Describe what actually happened here.
3.306 - critical: Error loading text-to-speech plug-in "speechd" (default:unknown:0)

Steps To Reproduce

1. Create linux mint 22.1 instance.
2. Run latest qgroundcontrol.

Additional Details
Add any extra info (errors, warnings, etc.) here.

System Information

.-MMMM`..-:::::::-..`MMMM-.          OS: Linux Mint 22 x86_64 
.:MMMM.:MMMMMMMMMMMMMMM:.MMMM:.        Host: ROG Zephyrus G14 GA403UI_GA403UI 1.0 

-MMM-M---MMMMMMMMMMMMMMMMMMM.MMM- Kernel: 6.14.0-35-generic
:MMM:MM :MMMM:....::-...-MMMM:MMM: Uptime: 15 mins :MMM:MMM :MM: `` `` :MMM:MMM: Packages: 3330 (dpkg), 15 (flatpak)
.MMM.MMMM :MM. -MM. .MM- MMMM.MMM. Shell: bash 5.2.21
:MMM:MMMM :MM. -MM- .MM: MMMM-MMM: Resolution: 2880x1800
:MMM:MMMM :MM. -MM- .MM: MMMM:MMM: DE: Cinnamon 6.2.9
:MMM:MMMM :MM. -MM- .MM: MMMM-MMM: WM: Mutter (Muffin)
.MMM.MMMM :MM:--:MM:--:MM: MMMM.MMM. WM Theme: Mint-Y-Dark-Aqua (Mint-Y)
:MMM:MMM- -MMMMMMMMMMMM- -MMM-MMM: Theme: Mint-Y-Aqua [GTK2/3]
:MMM:MMM: :MMM:MMM: Icons: Mint-Y-Sand [GTK2/3]
.MMM.MMMM:--------------:MMMM.MMM. Terminal: gnome-terminal
'-MMMM.-MMMMMMMMMMMMMMM-.MMMM-' CPU: AMD Ryzen 9 8945HS w/ Radeon 780M Graphics (16) @ 5.263GHz
'.-MMMM--:::::--MMMM-.' GPU: AMD ATI 65:00.0 Phoenix3
'-MMMMMMMMMMMMM-' GPU: NVIDIA GeForce RTX 4070 Max-Q / Mobile
-:::::- Memory: 2642MiB / 31378MiB

Log Files and Screenshots

No response</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Text to speech does not work on Linux Mint 22.1. #13643

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