Fix ESLint errors, bugs, and add gravity export

- Fix missing return in childRegistrationUtils.registerChild()
- Fix assertionUtils: assertNoNaN uses this.assertNoNaN
- Fix logger: nameModule uses this.nameModule
- Fix assetUtils: convert ESM to CommonJS
- Fix childRegistrationUtils_DEPRECATED: desc -> softwareType
- Add gravity export to index.js for rotatingMachine
- Fix ESLint errors across 18 files (no-undef, no-case-declarations,
  no-mixed-spaces-and-tabs, parsing errors)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/predict/interpolation.js

@@ -101,6 +101,7 @@ class Interpolation {
     } else if (type == "monotone_cubic_spline") {
       this.monotonic_cubic_spline();
     } else if (type == "linear") {
+      /* intentionally empty */
     } else {
       this.error = 1000;
     }
@@ -266,6 +267,7 @@ class Interpolation {
     let k = 0;
 
     if (xpoint < xdata[0] || xpoint > xdata[n - 1]) {
+      /* intentionally empty */
     }
 
     while (k < n - 1 && xpoint > xdata[k + 1] && !(xpoint < xdata[0] || xpoint > xdata[n - 1])) {