refactor: move .glsl files to /glsl

[birkskyum]

In preparation for other shader formats (mainly WGSL), this PR moves the GLSL files from /shaders to /shaders/glsl/

Related to

• [PoC] WebGPU Backend #7411
• WebGPU support #2606

Launch Checklist

• Confirm your changes do not include backports from Mapbox projects (unless with compliant license) - if you are not sure about this, please ask!
• Briefly describe the changes in this PR.
• Link to related issues.
• Include before/after visuals or gifs if this PR includes visual changes.
• Write tests for all new functionality.
• Document any changes to public APIs.
• Post benchmark scores.
• Add an entry to CHANGELOG.md under the ## main section.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.59%. Comparing base (789b3da) to head (cbb5206).
⚠️ Report is 5 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7418      +/-   ##
==========================================
- Coverage   92.86%   92.59%   -0.28%     
==========================================
  Files         288      288              
  Lines       23998    23998              
  Branches     5095     5095              
==========================================
- Hits        22286    22221      -65     
- Misses       1712     1777      +65     

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[Copilot]

Pull request overview

This PR reorganizes the shader source layout by moving GLSL files under src/shaders/glsl/, updating build/test tooling and references accordingly to prepare for adding additional shader formats (e.g., WGSL) alongside GLSL.

Changes:

• Move GLSL shader sources into src/shaders/glsl/.
• Update shader imports (src/shaders/shaders.ts) and shader codegen (build/generate-shaders.ts) to use the new location.
• Update tests and example references to point at the new GLSL path.

Reviewed changes

Copilot reviewed 4 out of 75 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
test/examples/add-a-simple-custom-layer-on-a-globe.html	Update example comment to reference new GLSL projection path.
test/build/shaders.test.ts	Update shader glob path to the new GLSL directory.
src/shaders/shaders.ts	Update all generated-shader imports to ./glsl/*.
build/generate-shaders.ts	Update shader discovery/output paths to src/shaders/glsl.
src/shaders/glsl/_prelude.fragment.glsl	Relocated GLSL prelude fragment source.
src/shaders/glsl/_prelude.vertex.glsl	Relocated GLSL prelude vertex source.
src/shaders/glsl/_projection_globe.vertex.glsl	Relocated globe projection helper shader.
src/shaders/glsl/_projection_mercator.vertex.glsl	Relocated mercator projection helper shader.
src/shaders/glsl/atmosphere.fragment.glsl	Relocated atmosphere fragment shader.
src/shaders/glsl/atmosphere.vertex.glsl	Relocated atmosphere vertex shader.
src/shaders/glsl/background.fragment.glsl	Relocated background fragment shader.
src/shaders/glsl/background.vertex.glsl	Relocated background vertex shader.
src/shaders/glsl/background_pattern.fragment.glsl	Relocated background-pattern fragment shader.
src/shaders/glsl/background_pattern.vertex.glsl	Relocated background-pattern vertex shader.
src/shaders/glsl/circle.fragment.glsl	Relocated circle fragment shader.
src/shaders/glsl/circle.vertex.glsl	Relocated circle vertex shader.
src/shaders/glsl/clipping_mask.fragment.glsl	Relocated clipping-mask fragment shader.
src/shaders/glsl/clipping_mask.vertex.glsl	Relocated clipping-mask vertex shader.
src/shaders/glsl/collision_box.fragment.glsl	Relocated collision-box fragment shader.
src/shaders/glsl/collision_box.vertex.glsl	Relocated collision-box vertex shader.
src/shaders/glsl/collision_circle.fragment.glsl	Relocated collision-circle fragment shader.
src/shaders/glsl/collision_circle.vertex.glsl	Relocated collision-circle vertex shader.
src/shaders/glsl/color_relief.fragment.glsl	Relocated color-relief fragment shader.
src/shaders/glsl/color_relief.vertex.glsl	Relocated color-relief vertex shader.
src/shaders/glsl/debug.fragment.glsl	Relocated debug fragment shader.
src/shaders/glsl/debug.vertex.glsl	Relocated debug vertex shader.
src/shaders/glsl/depth.vertex.glsl	Relocated depth-only vertex shader.
src/shaders/glsl/fill.fragment.glsl	Relocated fill fragment shader.
src/shaders/glsl/fill.vertex.glsl	Relocated fill vertex shader.
src/shaders/glsl/fill_extrusion.fragment.glsl	Relocated fill-extrusion fragment shader.
src/shaders/glsl/fill_extrusion.vertex.glsl	Relocated fill-extrusion vertex shader.
src/shaders/glsl/fill_extrusion_pattern.fragment.glsl	Relocated fill-extrusion-pattern fragment shader.
src/shaders/glsl/fill_extrusion_pattern.vertex.glsl	Relocated fill-extrusion-pattern vertex shader.
src/shaders/glsl/fill_outline.fragment.glsl	Relocated fill-outline fragment shader.
src/shaders/glsl/fill_outline.vertex.glsl	Relocated fill-outline vertex shader.
src/shaders/glsl/fill_outline_pattern.fragment.glsl	Relocated fill-outline-pattern fragment shader.
src/shaders/glsl/fill_outline_pattern.vertex.glsl	Relocated fill-outline-pattern vertex shader.
src/shaders/glsl/fill_pattern.fragment.glsl	Relocated fill-pattern fragment shader.
src/shaders/glsl/fill_pattern.vertex.glsl	Relocated fill-pattern vertex shader.
src/shaders/glsl/heatmap.fragment.glsl	Relocated heatmap fragment shader.
src/shaders/glsl/heatmap.vertex.glsl	Relocated heatmap vertex shader.
src/shaders/glsl/heatmap_texture.fragment.glsl	Relocated heatmap-texture fragment shader.
src/shaders/glsl/heatmap_texture.vertex.glsl	Relocated heatmap-texture vertex shader.
src/shaders/glsl/hillshade.fragment.glsl	Relocated hillshade fragment shader.
src/shaders/glsl/hillshade.vertex.glsl	Relocated hillshade vertex shader.
src/shaders/glsl/hillshade_prepare.fragment.glsl	Relocated hillshade-prepare fragment shader.
src/shaders/glsl/hillshade_prepare.vertex.glsl	Relocated hillshade-prepare vertex shader.
src/shaders/glsl/line.fragment.glsl	Relocated line fragment shader.
src/shaders/glsl/line.vertex.glsl	Relocated line vertex shader.
src/shaders/glsl/line_gradient.fragment.glsl	Relocated line-gradient fragment shader.
src/shaders/glsl/line_gradient.vertex.glsl	Relocated line-gradient vertex shader.
src/shaders/glsl/line_gradient_sdf.fragment.glsl	Relocated line-gradient-sdf fragment shader.
src/shaders/glsl/line_gradient_sdf.vertex.glsl	Relocated line-gradient-sdf vertex shader.
src/shaders/glsl/line_pattern.fragment.glsl	Relocated line-pattern fragment shader.
src/shaders/glsl/line_pattern.vertex.glsl	Relocated line-pattern vertex shader.
src/shaders/glsl/line_sdf.fragment.glsl	Relocated line-sdf fragment shader.
src/shaders/glsl/line_sdf.vertex.glsl	Relocated line-sdf vertex shader.
src/shaders/glsl/projection_error_measurement.fragment.glsl	Relocated projection error measurement fragment shader.
src/shaders/glsl/projection_error_measurement.vertex.glsl	Relocated projection error measurement vertex shader.
src/shaders/glsl/raster.fragment.glsl	Relocated raster fragment shader.
src/shaders/glsl/raster.vertex.glsl	Relocated raster vertex shader.
src/shaders/glsl/sky.fragment.glsl	Relocated sky fragment shader.
src/shaders/glsl/sky.vertex.glsl	Relocated sky vertex shader.
src/shaders/glsl/symbol_icon.fragment.glsl	Relocated symbol-icon fragment shader.
src/shaders/glsl/symbol_icon.vertex.glsl	Relocated symbol-icon vertex shader.
src/shaders/glsl/symbol_sdf.fragment.glsl	Relocated symbol-sdf fragment shader.
src/shaders/glsl/symbol_sdf.vertex.glsl	Relocated symbol-sdf vertex shader.
src/shaders/glsl/symbol_text_and_icon.fragment.glsl	Relocated symbol-text-and-icon fragment shader.
src/shaders/glsl/symbol_text_and_icon.vertex.glsl	Relocated symbol-text-and-icon vertex shader.
src/shaders/glsl/terrain.fragment.glsl	Relocated terrain fragment shader.
src/shaders/glsl/terrain.vertex.glsl	Relocated terrain vertex shader.
src/shaders/glsl/terrain_coords.fragment.glsl	Relocated terrain-coords fragment shader.
src/shaders/glsl/terrain_coords.vertex.glsl	Relocated terrain-coords vertex shader.
src/shaders/glsl/terrain_depth.fragment.glsl	Relocated terrain-depth fragment shader.
src/shaders/glsl/terrain_depth.vertex.glsl	Relocated terrain-depth vertex shader.

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