feat: add more shader group diagnostics to compile_report

[lgritz]

When compile_report >= 1, report several new post-optimization stats for the shader group:

• Number of active (non-unused) layers
• Maximum connection depth of the shader network (node count along the longest layer-to-layer chain, so a single unconnected node = 1 and a chain A->B->C = 3)
• Number of texture ops (texture, environment, gettextureinfo, texture3d)
• Number of noise ops

Note that these stats (number of layers, texture ops, noise ops) are the total number in the post-optimized shader, but not the number that will be run on any particular execution of the shader. Trivial example: the noise calls may all be inside an "if" statement with a condition that is never true in practice, but that can't be known ahead of time. In the other direction, a loop with noise calls in the body will underestimate how many calls are made in each shader run. So take with a grain of salt -- these stats are related overall shader code complexity, but not necessarily to execution cost.

Coded via pair programming with Claude Code, using the Claude Sonnet 4.6 model.

[lgritz]

Hang on, don't review yet; I want to add one more stat, testing now.

[lgritz]

Amended to also count the number of noise calls in the post-optimized shader. Ok to review now.

[fpsunflower]

LGTM

Would be curious to see the types of results you get from your production shaders ...

[lgritz]

Would be curious to see the types of results you get from your production shaders ...

The use is speculative, and may be subject to further refinement. I think we're looking for some way to leave breadcrumbs behind in the logs so that when a render is absurdly expensive, people can make a good guess about whether there is any particular material that looks so out of whack that maybe it's a possible culprit.