fix(design): rating and live colour tokens, the player's menus over its notices, the info overlay on a light theme (E28)

- F16: --rating (theme-scoped gold, 4.5:1 on the page and its chip), --rating-media, --live/--live-fg,
  --media-chrome replace 14 palette literals; a lint rule refuses palette classes; the theme contract
  measures them.
- The Plex player's notices drew over its open settings/tracks popovers: notices z-base, popovers z-menu.
- The player's info overlay rendered theme tokens on its always-dark panel: on a light theme the score
  (2.6:1), collection years (3.2:1) and cast initials (1.05:1) were unreadable; onDark variants now.
- The lint-rule contract tests share one ESLint with a one-off warm-up (a cold first lint took 8 s,
  past vitest's 5 s).

frontend/src/lib/uiBoundary.contract.test.ts

@@ -1,8 +1,7 @@
-import { fileURLToPath } from "node:url";
-
-import { ESLint } from "eslint";
 import { describe, expect, it } from "vitest";
 
+import { eslint } from "./lintProbe.testkit";
+
 // E10 S1 declared `components/ui/` a platform layer and put the rule that makes it one — no feature
 // components, no domain API slices — into eslint.config.js rather than prose. This asserts the rule
 // actually FIRES, because a `no-restricted-imports` pattern that matches nothing is indistinguishable
@@ -18,10 +17,8 @@ const AS_UI = "src/components/ui/__boundary_probe.tsx";
 
 // fileURLToPath, not URL.pathname: on Windows the latter yields "/D:/…", which eslint cannot resolve
 // a config from. Anchored to this file rather than process.cwd() so the test holds wherever it is run.
-const FRONTEND = fileURLToPath(new URL("../../", import.meta.url));
 
 async function restrictedIn(source: string, filePath: string): Promise<string[]> {
-  const eslint = new ESLint({ cwd: FRONTEND });
   const [result] = await eslint.lintText(source, { filePath });
   return (result?.messages ?? []).filter((m) => m.ruleId === BOUNDARY).map((m) => m.message);
 }