Improved spectrogram by using the RHI

[kunitoki]

This pull request introduces several significant improvements and fixes across the DSP, UI, and audio GUI components. The most notable changes are the introduction of double-precision support in the FFTProcessor, major GPU optimizations and accuracy improvements in the SpectrogramComponent, and a new repaint mode for UI components that optimizes partial redraws. Additionally, several bug fixes and documentation updates were made to reflect these enhancements.

DSP and FFTProcessor Improvements:

• FFTProcessor is now templated on the sample type (float or double), with all backends supporting native double-precision paths. The public API now accepts buffers with any alignment, and references to the scaling enum must be qualified (e.g., FFTProcessor<float>::FFTScaling::asymmetric). [1] [2] [3] [4] [5]
• Fixed the Ooura FFT double-precision backend build on all platforms by moving helper declarations to namespace scope.

Audio GUI (yup_audio_gui) Enhancements:

• SpectrogramComponent now keeps its waterfall history on the GPU, using a precompiled shader bundle for efficient rendering. The scroll speed is adjustable, and the log-frequency to FFT-bin mapping is precomputed for performance. The component now requires a GPU render context.
• Waterfall scroll is now framerate-independent, draining FFT rows over multiple passes if needed, and can be paused accurately. Failures are now reported via Logger::outputDebugString, and render resolution is exposed via a new constant.
• SpectrumAnalyzerComponent and SpectrogramComponent now use a new SpectrumBinMapping for continuous, accurate log-frequency display, with improved interpolation and aggregation over bands.
• Fixed a readiness bug in SpectrumAnalyzerState so that FFT data is available immediately after a bulk push.
• SpectrumAnalyzerComponent now generates its spectrum outline per pixel column for smooth, continuous curves at any resolution.

UI and Graphics Updates:

• Introduced ComponentNative::RepaintMode, allowing selection between repainting disjoint dirty rectangles (default) or a single bounding box for backward compatibility. Documentation updated to explain the new mode. [1] [2]
• SDL windowing now expands dirty areas by half a pixel to prevent persistent lines from anti-aliased clips, addressing visual artifacts in continuously repainting components.

Other Fixes and Minor Changes:

• Noise generation in SignalGenerator was refactored for clarity and correctness, using a common generateWhiteNoise() method and clamping brown noise output. [1] [2]
• Minor code and documentation cleanups, including atomic header inclusion and removal of direct Ooura FFT documentation in favor of FFTProcessor. [1] [2]

These changes collectively improve performance, accuracy, and usability in both DSP and UI components.

[codecov]

Codecov Report

❌ Patch coverage is 68.06387% with 160 lines in your changes missing coverage. Please review.
✅ Project coverage is 82.21%. Comparing base (97d7da7) to head (702491b).

Files with missing lines	Patch %	Lines
...up_audio_gui/displays/yup_SpectrogramComponent.cpp	44.23%	116 Missing ⚠️
.../yup_audio_gui/displays/yup_SpectrumBinMapping.cpp	82.40%	19 Missing ⚠️
...dio_gui/displays/yup_SpectrumAnalyzerComponent.cpp	71.42%	16 Missing ⚠️
modules/yup_dsp/frequency/yup_FFTProcessor.cpp	94.87%	4 Missing ⚠️
modules/yup_gui/component/yup_Component.cpp	93.93%	2 Missing ⚠️
.../yup_audio_gui/displays/yup_SpectrogramComponent.h	50.00%	1 Missing ⚠️
...es/yup_audio_gui/displays/yup_SpectrumBinMapping.h	66.66%	1 Missing ⚠️
...es/yup_dsp/frequency/yup_SpectrumAnalyzerState.cpp	87.50%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #174      +/-   ##
==========================================
+ Coverage   82.06%   82.21%   +0.14%     
==========================================
  Files         818      820       +2     
  Lines       87399    87623     +224     
==========================================
+ Hits        71720    72035     +315     
+ Misses      15679    15588      -91     

Files with missing lines	Coverage Δ
...audio_gui/displays/yup_SpectrumAnalyzerComponent.h	92.30% <ø> (ø)
...p_audio_processors/spectral/yup_SpectralBridge.cpp	84.44% <100.00%> (ø)
...yup_audio_processors/spectral/yup_SpectralBridge.h	83.33% <ø> (ø)
...s/yup_dsp/convolution/yup_PartitionedConvolver.cpp	92.92% <100.00%> (ø)
modules/yup_dsp/frequency/yup_FFTProcessor.h	66.66% <ø> (+16.66%)	⬆️
modules/yup_dsp/onsets/yup_Spectrogram.h	100.00% <ø> (ø)
modules/yup_gui/component/yup_Component.h	76.00% <ø> (ø)
modules/yup_gui/component/yup_ComponentNative.cpp	100.00% <100.00%> (ø)
modules/yup_gui/component/yup_ComponentNative.h	33.33% <ø> (ø)
.../yup_audio_gui/displays/yup_SpectrogramComponent.h	85.71% <50.00%> (-6.60%)	⬇️
... and 7 more

... and 9 files with indirect coverage changes

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