fix(i18n): every label a screen reader or tooltip says is translated

- The Plex playlist rows' "reorder"/"remove", the Plex filter chip's "remove" and the player
  slider's "reset" were English literals; each now names its row or setting in HU/EN.
- The playlist show header's chevron had no accessible name; its decorative thumbnail button left
  the tab order.
- The opt-in Glass tuner panel was English only: every word is translated, and each slider's label
  now names its number box and range.
- New `local/literal-a11y-text` lint rule (with its contract test): a literal word in aria-label,
  title, placeholder, alt and the other spoken/shown attributes fails lint.

frontend/eslint.config.js

@@ -82,8 +82,52 @@ const focusSafeDisabled = {
     };
   },
 };
+// The words a screen reader or a tooltip says are user-facing text like any other, and the HU/EN
+// parity rule covers them too. Five `aria-label="remove"`-style literals survived every lane (the
+// Plex playlist rows, a filter chip, the player's reset) and a whole opt-in panel was English only —
+// nothing looks at an attribute. A URL-shaped placeholder is not a word, so it passes.
+const A11Y_TEXT = new Set([
+  "aria-label",
+  "aria-description",
+  "aria-placeholder",
+  "aria-roledescription",
+  "aria-valuetext",
+  "title",
+  "placeholder",
+  "alt",
+]);
+const literalText = (v) => {
+  if (!v) return null;
+  if (v.type === "Literal") return typeof v.value === "string" ? v.value : null;
+  if (v.type !== "JSXExpressionContainer") return null;
+  const e = v.expression;
+  if (e.type === "Literal") return typeof e.value === "string" ? e.value : null;
+  if (e.type === "TemplateLiteral" && e.expressions.length === 0) return e.quasis[0].value.cooked;
+  return null;
+};
+const literalA11yText = {
+  meta: {
+    type: "problem",
+    messages: { literal: "`{{name}}` is read or shown to the user: translate it with t()." },
+  },
+  create(context) {
+    return {
+      JSXAttribute(node) {
+        const name = node.name.type === "JSXIdentifier" ? node.name.name : null;
+        if (!name || !A11Y_TEXT.has(name)) return;
+        const text = literalText(node.value);
+        if (text && /[A-Za-z]{2,}/.test(text) && !/^https?:/.test(text))
+          context.report({ node, messageId: "literal", data: { name } });
+      },
+    };
+  },
+};
 const localRules = {
-  rules: { "jsx-comment-text": jsxCommentText, "focus-safe-disabled": focusSafeDisabled },
+  rules: {
+    "jsx-comment-text": jsxCommentText,
+    "focus-safe-disabled": focusSafeDisabled,
+    "literal-a11y-text": literalA11yText,
+  },
 };
 
 // A px-frozen BOX utility (the no-restricted-syntax block below): an esquery regex, as a string.
@@ -113,6 +157,7 @@ export default tseslint.config(
       ...reactHooks.configs.recommended.rules,
       "local/jsx-comment-text": "error",
       "local/focus-safe-disabled": "error",
+      "local/literal-a11y-text": "error",
       "react-refresh/only-export-components": ["warn", { allowConstantExport: true }],
       // tsc already enforces these under strict + noUnusedLocals/Parameters — let it own them so a
       // finding is reported once, by one tool, and this config stays about hooks + refresh safety.
@@ -237,8 +282,13 @@ export default tseslint.config(
   },
   {
     // Tests stand doubles in for the network (`vi.stubGlobal("fetch", …)`) and may reach it directly.
+    // …and render throwaway markup whose labels no user ever hears.
     files: ["src/**/*.test.{ts,tsx}"],
-    rules: { "no-restricted-globals": "off", "no-restricted-properties": "off" },
+    rules: {
+      "no-restricted-globals": "off",
+      "no-restricted-properties": "off",
+      "local/literal-a11y-text": "off",
+    },
   },
   prettier,
 );