chore(a11y): enforce a curated jsx-a11y lint gate in CI (P3-4)

Enables ARIA-correctness rules (aria-props/proptypes/role/unsupported-elements,
role-has/supports-aria-props, no-redundant-roles, anchor/heading-has-content)
+ label-has-associated-control as errors — a regression gate for accessible
names + valid ARIA. control-has-associated-label deliberately NOT enabled (the
repo's <Text as="label" htmlFor> component pattern defeats its static analysis);
the real gaps it surfaced were fixed directly. Also disable max-classes-per-file
for test files (mock classes).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

eslint.config.mjs

@@ -25,7 +25,7 @@ export default [
   tsPlugin.configs['flat/eslint-recommended'],
   ...tsPlugin.configs['flat/recommended'],
   reactPlugin.configs.flat.recommended,
-  reactHooksPlugin.configs.flat['recommended'],
+  reactHooksPlugin.configs.flat.recommended,
   // Register jsx-a11y plugin (rules selectively enabled below)
   { plugins: { 'jsx-a11y': jsxA11yPlugin } },
   // airbnb-base via FlatCompat (JS/import rules; no React plugin, no getFilename issue)
@@ -115,6 +115,26 @@ export default [
       'jsx-a11y/media-has-caption': 'off',
       'jsx-a11y/no-noninteractive-element-interactions': 'off',
       'jsx-a11y/alt-text': 'off',
+      // A11y regression gate (P3-4). A CURATED set — correctness rules that catch
+      // real WCAG gaps (missing accessible names, malformed ARIA) without
+      // flooding on the pre-existing clickable-div patterns. The heavier
+      // interaction rules (no-static-element-interactions,
+      // click-events-have-key-events) are a separate cleanup and stay OFF.
+      'jsx-a11y/aria-props': 'error',
+      'jsx-a11y/aria-proptypes': 'error',
+      'jsx-a11y/aria-role': ['error', { ignoreNonDOM: true }],
+      'jsx-a11y/aria-unsupported-elements': 'error',
+      'jsx-a11y/role-has-required-aria-props': 'error',
+      'jsx-a11y/role-supports-aria-props': 'error',
+      'jsx-a11y/no-redundant-roles': 'error',
+      'jsx-a11y/anchor-has-content': 'error',
+      'jsx-a11y/heading-has-content': 'error',
+      'jsx-a11y/label-has-associated-control': ['error', { assert: 'either', depth: 5 }],
+      // NOT enabled: control-has-associated-label. This repo labels most inputs
+      // with folds `<Text as="label" htmlFor>` — a component the rule's static
+      // analysis can't see as a <label>, producing false positives on correctly
+      // labeled controls. The genuinely-unlabeled controls it surfaced (sliders,
+      // file input, media players, notes) were fixed directly with aria-label.
     },
   },
   {
@@ -123,4 +143,11 @@ export default [
       'no-undef': 'off',
     },
   },
+  {
+    // Test files commonly define several small mock/fake classes.
+    files: ['**/*.test.ts', '**/*.test.tsx'],
+    rules: {
+      'max-classes-per-file': 'off',
+    },
+  },
 ];