fix(astro): support stricter optional property checking (#5070)

Omit absent className values when calling the shared icon builder so
shipped Astro source passes exactOptionalPropertyTypes without changing
rendered classes.

Enable exactOptionalPropertyTypes and noUncheckedIndexedAccess in the
package tsconfig so the existing CI typecheck catches regressions.

Background: https://github.com/withastro/astro/issues/18471

Co-authored-by: Codex <noreply@openai.com>
Co-authored-by: Eric Fennis <eric.fennis@gmail.com>

packages/astro/src/Icon.astro

@@ -28,7 +28,7 @@ const [, builtIconAttributes, builtIconNode = []] = buildLucideIconNode(icon, {
   strokeWidth,
   absoluteStrokeWidth,
   nonScalingStroke,
-  className,
+  ...(className !== undefined && { className }),
   hasA11yProp: hasA11yProp(rest),
 });
 

packages/astro/tsconfig.json

@@ -4,6 +4,8 @@
     "module": "ESNext",
     "moduleResolution": "bundler",
     "strict": true,
+    "noUncheckedIndexedAccess": true,
+    "exactOptionalPropertyTypes": true,
     "useDefineForClassFields": true,
     "allowImportingTsExtensions": true,
     "resolveJsonModule": true,