Merge PR #1023: preserve minified text strokes

Keep adaptive sampling in both text shaders with compact sampling loops. Validate shader derivatives and existing text rendering, including GPU pipeline creation.

Closes #964

tests/text_shader_minification.rs

@@ -0,0 +1,16 @@
+#[test]
+fn adaptive_text_sampling_passes_derivative_uniformity_validation() {
+    for (name, source) in [
+        ("text", include_str!("../src/shaders/text.wgsl")),
+        ("block text", include_str!("../src/shaders/block_text.wgsl")),
+    ] {
+        let module = naga::front::wgsl::parse_str(source)
+            .unwrap_or_else(|error| panic!("{name}: {}", error.emit_to_string(source)));
+        naga::valid::Validator::new(
+            naga::valid::ValidationFlags::all(),
+            naga::valid::Capabilities::empty(),
+        )
+        .validate(&module)
+        .unwrap_or_else(|error| panic!("{name}: {error:?}"));
+    }
+}