feat(API): add destroyQmlApplicationEngine plugin hook (5.1)

[DonLakeFlyer]

Cherry-pick of #14787 to Stable_V5.1.

Verified locally on this branch: full Debug build passes.

[codecov]

Codecov Report

❌ Patch coverage is 50.00000% with 3 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (Stable_V5.1@249ac77). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
src/QGCApplication.cc	0.00%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@              Coverage Diff               @@
##             Stable_V5.1   #14805   +/-   ##
==============================================
  Coverage               ?   32.74%           
==============================================
  Files                  ?      784           
  Lines                  ?    67608           
  Branches               ?    31313           
==============================================
  Hits                   ?    22135           
  Misses                 ?    30579           
  Partials               ?    14894           

Flag	Coverage Δ
unittests	32.74% <50.00%> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
src/API/QGCCorePlugin.cc	43.23% <100.00%> (ø)
src/API/QGCCorePlugin.h	72.72% <ø> (ø)
src/QGCApplication.cc	22.80% <0.00%> (ø)

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[github-actions]

Build Results

Platform Status

Platform	Status	Details
Linux	Passed	View
Windows	Passed	View
MacOS	Passed	View
Android	Passed	View

All builds passed.

Pre-commit

Check	Status	Details
pre-commit	Failed (non-blocking)	View

Pre-commit hooks: 0 passed, 0 failed, 0 skipped.

Test Results

linux-coverage-integration: 37 passed, 0 skipped
linux-coverage-unit: 119 passed, 0 skipped
linux-sanitizers-integration: 20 passed, 0 skipped
linux-sanitizers-unit: 119 passed, 0 skipped
Total: 295 passed, 0 skipped

Code Coverage

Coverage: 69.5%

No baseline available for comparison

Artifact Sizes

Artifact	Size
QGroundControl	221.79 MB
QGroundControl-aarch64	179.36 MB
QGroundControl-installer-AMD64	137.87 MB
QGroundControl-installer-AMD64-ARM64	80.38 MB
QGroundControl-installer-ARM64	109.11 MB
QGroundControl-linux	87.04 MB
QGroundControl-mac	87.04 MB
QGroundControl-x86_64	191.58 MB
No baseline available for comparison

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_{Updated: 2026-08-09 17:09:23 UTC • Commit: cf1067c • Triggered by: Windows}