Reduce egraph saturation iterations to limit growth for complex shaders

Lower the iteration count from 10 to 8 to prevent OOM/stack overflow
on matrix-heavy and deeply nested shaders (e.g. sky-shader). Most
optimizations converge within 4-6 iterations; the extra headroom was
causing exponential e-graph growth with matrix decomposition rules.

Author: LegNeato

rust/spirv-tools-opt/src/direct/mod.rs

@@ -841,7 +841,7 @@ pub fn optimize_module_direct(module: &Module) -> Result<Module, EgglogOptError>
     // - DCE-aware constant folding (dead branches are identified)
     // - Partial DCE (RVSDG Gamma/Theta branches marked dead when condition is constant)
     // - Optimizations that expose new DCE opportunities
-    let run_cmd = "(run-schedule (repeat 10 (run)))";
+    let run_cmd = "(run-schedule (repeat 8 (run)))";
     egraph
         .parse_and_run_program(None, run_cmd)
         .map_err(|e| EgglogOptError::ExecutionError(e.to_string()))?;