fix(contributors): address Copilot review comments and code quality issues

- Improve contributor-report.mjs based on Copilot comments and sonar
- Use fileURLToPath for Windows-safe main checks in contributor scripts
- Fix README badge URLs by removing duplicate style parameters
- Update graceful-shutdown.mjs to throw on process.exit failure for better error visibility

Generated-by: GitHub Copilot <copilot@github.com>
Signed-off-by: Ashley Childress <6563688+anchildress1@users.noreply.github.com>

eng/add-missing-contributors.mjs

@@ -8,6 +8,7 @@
 import { execSync } from 'node:child_process';
 import fs from 'node:fs';
 import path from 'node:path';
+import { fileURLToPath } from 'node:url';
 import {
   getContributionTypes,
   getMissingContributors,
@@ -282,7 +283,7 @@ const printSummaryReport = (results) => {
   console.log('\n' + '='.repeat(50));
 };
 
-if (process.argv[1] === (new URL(import.meta.url)).pathname) {
+if (process.argv[1] && fileURLToPath(import.meta.url) === path.resolve(process.argv[1])) {
   try {
     const results = await main();
     printSummaryReport(results);