fix: viewer.js string entry handling + HLS console log for integration tests

- Handle string entries in createPanel (e.g. 'https://...mp4')
  instead of dropping them as null — restores legacy string URL support.
- Add console.log for HLS detection so integration tests can verify
  HLS playback paths are exercised.

eslint.config.js

@@ -0,0 +1,24 @@
+// ESLint flat config — v9+
+import globals from 'globals';
+
+export default [
+  {
+    ignores: ['dist/', 'node_modules/'],
+  },
+  {
+    files: ['**/*.js', '**/*.mjs'],
+    languageOptions: {
+      ecmaVersion: 2024,
+      sourceType: 'module',
+      globals: {
+        ...globals.browser,
+        ...globals.es2024,
+        chrome: 'readonly',
+      },
+    },
+    rules: {
+      'no-unused-vars': ['warn', { argsIgnorePattern: '^_' }],
+      'no-console': 'off',
+    },
+  },
+];