feat(scripts): cached plugin bundle, single-plugin fetch, free-chapter prefix, nightly appender

- load-plugins: bundle once per source revision with an id index; loadPlugin(id)
  loads one plugin (144 ms / 87 MB instead of ~15 s / 1.2 GB).
- fetch-novel: keep only the contiguous run of free chapters (no locked teasers).
- update-novels: append newly free chapters to our EPUBs without moving positions.
- find-novel --json for programs; shared EPUB pieces in epub.js.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

scripts/find-novel.js

@@ -1,13 +1,16 @@
 // Search every plugin of the given languages for a title and list the sources
-// that carry it. Usage: node scripts/find-novel.js "<title>" [lang...]
-// Languages are plugin folder names (default: english multi).
+// that carry it. Usage: node scripts/find-novel.js [--json] "<title>" [lang...]
+// Languages are plugin folder names (default: english multi). --json prints one JSON
+// array of {source, id, name, path, url, exact} for programs (the request page).
 import { loadPlugins, print } from './load-plugins.js';
 
 const TIMEOUT_MS = 20_000;
 const CONCURRENCY = 16;
 const PER_SOURCE = 3;
 
-const [term, ...langArgs] = process.argv.slice(2);
+const args = process.argv.slice(2);
+const asJson = args[0] === '--json';
+const [term, ...langArgs] = asJson ? args.slice(1) : args;
 if (!term) {
   console.error('Usage: node scripts/find-novel.js "<title>" [lang...]');
   process.exit(2);
@@ -64,6 +67,10 @@ const matches = hits.filter(h =>
 const rank = h => (norm(h.name) === exact ? 0 : 1);
 matches.sort((a, b) => rank(a) - rank(b) || a.source.localeCompare(b.source));
 
+if (asJson) {
+  print(JSON.stringify(matches.map(h => ({ ...h, exact: rank(h) === 0 }))));
+  process.exit(0);
+}
 for (const h of matches) {
   print(
     `${rank(h) === 0 ? '*' : ' '} ${h.source.padEnd(28)} ${h.name}\n` +