fix(flame_3d): Use float for numLights uniform to fix GLES crash

[agnath18K]

Description

Fixes #3809

flame_3d crashes on Android GLES because spatial_material.frag declares uint numLights and lighting_info.dart sets it via shader.setUint(). Impeller's GLES backend only supports float uniforms — the uint path hits an unhandled shader type and crashes.

Changed uint → float in the shader and setUint → setFloat in Dart. The value is a light count (0–3) so float works identically. Recompiled the shaderbundle.

Checklist

• I have followed the Contributor Guide when preparing my PR.
• I have updated/added tests for ALL new/updated/fixed functionality.
• I have updated/added relevant documentation in docs and added dartdoc comments with ///.
• I have updated/added relevant examples in examples or docs.

No test added — the crash only reproduces on a real GLES device/emulator, not in unit tests. The existing lighting logic is unchanged; only the uniform type is corrected.

Breaking Change?

• Yes, this PR is a breaking change.
• No, this PR is not a breaking change.

[wolfenrain]

We should verify if this still works on iOS/macos

I don't mind changing it to an float, but if I recall we had weird float issues on the other platforms 😭

[luanpotter]

I tried on macos - it works!

[luanpotter]

@agnath18K thanks for your contribution and interest in flame_3d !

do you have a link or reference or github issue to explain "Impeller's GLES backend only supports float uniforms"? so we can add a small comment just for future reference

then I can do the bundle re-gen and merge!

[agnath18K]

@agnath18K thanks for your contribution and interest in flame_3d !

do you have a link or reference or github issue to explain "Impeller's GLES backend only supports float uniforms"? so we can add a small comment just for future reference

then I can do the bundle re-gen and merge!

hey @luanpotter , some references for the GLES float-only uniform limitation:
-> The check is in buffer_bindings_gles.cc — validates "Only float uniforms are supported", only calls glUniform*fv variants (engine/src/flutter/impeller/renderer/backend/gles/buffer_bindings_gles.cc)
-> Best example: flutter/engine#55329 — gaussian blur had to swap int sample_count →
float sample_count and cast back in the shader to work around it

https://docs.flutter.dev/ui/design/graphics/fragment-shaders
Related : flutter/engine#55329

[spydon]

With the extra info, lgtm!

[luanpotter]

Rebased and added a note in a comment