Fix squared/unicolor mean dispatch in both process overloads (fix #2057)

[Kirorus]

Summary

Fixes #2057.

mappingTypeToInt() and mappingTypeToStr() identify ID 1 as multicolor_mean_squared and ID 2 as unicolor_mean, but both process() template overloads call the opposite algorithms.

This PR corrects the four algorithm calls:

• ID 1 uses getMeanSqrtLedColor() (per-LED RMS).
• ID 2 uses getUniLedColor() (whole-image arithmetic mean repeated on all LEDs).
• ID 0 and dominant-color modes are unchanged.

Mapping names, numeric IDs, JSON schemas, API conversions, LED coordinates, black-border processing, and pixel averaging implementations are not changed.

Adds a small Python standard-library source-contract regression test covering all seven names, their stable IDs/reverse conversions, and the algorithm selections in both overloads. It intentionally does not claim to test pixel arithmetic or instantiate a native Qt daemon.

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update
• Refactor
• Docs
• Build-related changes
• Other, please describe:

If changing the UI of web configuration, please provide the before/after screenshot:

Not applicable: no UI change.

Does this PR introduce a breaking change?

• Yes
• No

No configuration schema or public API change. The two affected selections now perform their advertised algorithms. Users who intentionally selected the opposite label as a workaround will need to choose the correctly named mode after updating.

The PR fulfills these requirements:

• When resolving a specific issue, it's referenced in the PR's body (Fixes multicolor_mean_squared and unicolor_mean dispatch to swapped algorithms #2057).

If adding a new feature, the PR's description includes:

• A convincing reason for adding this feature
• Related documents have been updated (docs/docs/en)
• Related tests have been updated

Not applicable: this is a dispatch bugfix, not a new feature.

PLEASE DON'T FORGET TO ADD YOUR CHANGES TO CHANGELOG.MD

• Yes, CHANGELOG.md is also updated

Other information:

Verification

• python3 test/test_image_processor_mapping.py -v: 2 tests pass, with algorithm checks for all seven named modes in both overloads.
• The same test against the unmodified master implementation fails for both multicolor_mean_squared and unicolor_mean; stable name/ID round-trips pass. This establishes that the regression test catches the original mismatch.
• git diff --check: passes.
• Supplemental local C++ dispatch probe: the original name-conversion methods and both process template bodies were extracted unchanged and compiled with c++ -std=c++17 -Wall -Wextra -Werror -O2, using test doubles for Qt containers/logging, setup/border handling, and LED routines that report which algorithm was invoked. 26 checks / 4 failures on unmodified master; 26 checks / 0 failures with this fix. This is only dispatch validation, not a full Hyperion build or RGB calculation test.

The standalone source-contract test can be run with Python 3 from the repository root using the command above; it is not wired into the existing native test runner.

Validation limits

A full native Qt/Hyperion build was not run locally because the review host lacks CMake and Qt development packages. Repository CI and maintainer review are still needed. The patched daemon has not been installed or tested against real LED hardware. The live 2.2.1 observation and ordinary-mean workaround are documented separately in #2057; there is no claim of an already-deployed fix.

[hyperion-project]

Hello @Kirorus 👋

I'm the Hyperion Project Bot and I want to thank you for
contributing to Hyperion with your pull requests!

To help you and other users test your pull requests faster,
I'll create a link for you to your workflow artifacts.

🔗 https://github.com/hyperion-project/hyperion.ng/actions/runs/37353313393

Of course, if you make changes to your PR, I will create a new link.

Best regards,
Hyperion Project

[hyperion-project]

Hey @Kirorus I created a new link to your workflow artifacts:
🔗 https://github.com/hyperion-project/hyperion.ng/actions/runs/37831889393

[Lord-Grey]

@Kirorus Thank you for sharing your finding and already providing a fix via a PR.
This is very much appreciated.

PS: I used the opportunity to fix the tracing category in the file too :). Hope that is OK for you.