fix(memory): bound visualizer PCM cache and feed episode cache

The visualizer's PCM cache decoded the entire episode into RAM (22050 Hz
mono s16 ~160 MB/hr of audio) and held it until stop() — a 3-hour episode
pinned ~500 MB and long-form content hit 2.5 GB. The 4x decode also pulled
the whole remote file even when only minutes were listened to.

- audio-pcm-cache: sliding window around the playback position — the
  decode head caps at maxAheadSec (600s) ahead of the cursor, segments
  older than keepBehindSec (300s) are pruned, and the tail refills as
  playback advances. Steady state ~40 MB regardless of episode length;
  a backward seek past the window restarts a segment there (the existing
  seek-hole mechanism, no new failure mode).
- feed: cap the full-parse episode cache at 1000 episodes/feed so
  archive-heavy subscriptions can't pin their entire history in RAM;
  the visible list stays bounded by the user's cache preference and
  fetch-more keeps working within the ceiling.
- tests: pin the new head-cap and prune contracts (8/8 in
  audio-pcm-cache.test.ts; full suite 193 pass).

Also includes the in-flight cleanup/refactor pass (cover-art resolve
helper, page and comment tightening, ESLint config removal).

src/context/ThemeContext.tsx

@@ -10,7 +10,8 @@ import {
   generateSyntax,
   generateSubtleSyntax,
 } from "../utils/syntax-highlighter";
-import { resolveTerminalTheme, loadThemes } from "../utils/theme";
+import { resolveTerminalTheme } from "../utils/theme";
+import { getCustomThemes } from "../utils/custom-themes";
 import { detectModeFromBackground } from "../utils/system-theme";
 import { createSimpleContext } from "./helper";
 import {
@@ -175,7 +176,7 @@ export const { use: useTheme, provider: ThemeProvider } = createSimpleContext({
 
     function init() {
       resolveSystemTheme();
-      loadThemes()
+      getCustomThemes()
         .then((custom) => {
           setStore(
             produce((draft) => {
@@ -187,7 +188,6 @@ export const { use: useTheme, provider: ThemeProvider } = createSimpleContext({
           setStore("active", "catppuccin");
         })
         .finally(() => {
-          // Only set ready if not waiting for system theme
           if (store.active !== "system") {
             setStore("ready", true);
           }