feat(userscript): render Covers from the public route (#60)

Both userscripts stop scraping Covers and stop putting one on the wire.
A scraped address has no rendering path left now that the backend
acquires, stores and serves every Cover from its own origin (ADR-0007),
and keeping one would reintroduce third-party URLs into exactly the
place #47 came from.

- Adapters no longer read og:image / meta[name=image], and comix's
  img[alt] cover scan and novelfull's metaName helper are deleted.
- apiPut strips `cover` off every outgoing body, so a cached row's
  address (already ours) never travels back either. The server ignores
  the field regardless.
- Both card renderers swap in the existing `.cover.ph` placeholder when
  the image fails to load, so a failure looks designed rather than
  broken - the other half of what #47 reported.
- The deleted scraping's test cases go with it: the comix cover cases,
  the img[alt] and meta[name] stub branches, and the stale og:image
  fixtures. Export lists are unchanged; nothing cover-specific was
  exported.

The cover route itself is already public and uncredentialed, with the
immutable cache directive and 404-for-unknown covered by the tests that
landed with #59.

userscript/test/novel-logic.test.js

@@ -4,8 +4,7 @@ const test = require("node:test");
 const assert = require("node:assert");
 
 // ============================================================
-// Minimal browser stub. Same shape as logic.test.js, plus a meta[name=...]
-// branch: novelfull ships no og: tags, so its cover comes from name="image".
+// Minimal browser stub. Same shape as logic.test.js.
 // document.body stays UNDEFINED so the boot block waits for a DOMContentLoaded
 // that never fires and no network call is ever made.
 // ============================================================
@@ -20,20 +19,14 @@ globalThis.localStorage = {
 globalThis.location = { href: "about:blank", hostname: "", pathname: "/", origin: "" };
 
 let metaTags = {};
-let namedMetas = {};
 let elements = {};
 globalThis.document = {
   querySelector(sel) {
-    let m = sel.match(/^meta\[property="([^"]+)"\]$/);
+    const m = sel.match(/^meta\[property="([^"]+)"\]$/);
     if (m) {
       const v = metaTags[m[1]];
       return v == null ? null : { getAttribute: () => v };
     }
-    m = sel.match(/^meta\[name="([^"]+)"\]$/);
-    if (m) {
-      const v = namedMetas[m[1]];
-      return v == null ? null : { getAttribute: () => v };
-    }
     const text = elements[sel];
     return text == null ? null : { textContent: text };
   },
@@ -58,7 +51,6 @@ function loc(href) {
 
 function reset() {
   metaTags = {};
-  namedMetas = {};
   elements = {};
 }
 
@@ -68,21 +60,18 @@ function reset() {
 
 test("novelfull.detect reads a series page", () => {
   reset();
-  namedMetas = { image: "https://novelfull.com/uploads/thumbs/ri.jpg" };
   elements = { "h3.title": "Reverend Insanity" };
   const p = novelfull.detect(loc("https://novelfull.com/reverend-insanity.html"));
   assert.equal(p.type, "series");
   assert.equal(p.site, "novelfull");
   assert.equal(p.seriesId, "reverend-insanity");
   assert.equal(p.title, "Reverend Insanity");
-  assert.equal(p.cover, "https://novelfull.com/uploads/thumbs/ri.jpg");
   assert.equal(p.seriesUrl, "https://novelfull.com/reverend-insanity.html");
   assert.equal(p.chapterNum, null);
 });
 
 test("novelfull.detect reads a chapter page and points seriesUrl at the series", () => {
   reset();
-  namedMetas = { image: "https://novelfull.com/uploads/thumbs/ri.jpg" };
   elements = { "a.truyen-title": "Reverend Insanity" };
   const url = "https://novelfull.com/reverend-insanity/chapter-2334-fang-yuan.html";
   const p = novelfull.detect(loc(url));
@@ -120,14 +109,12 @@ test("novelfull.latestChapterFromAnchors takes the max and ignores other series"
 
 test("lightnovelworld.detect reads a series page", () => {
   reset();
-  metaTags = { "og:image": "https://lightnovelworld.net/wp-content/uploads/awe.webp" };
   elements = { "h1.entry-title": "A Will Eternal" };
   const p = lightnovelworld.detect(loc("https://lightnovelworld.net/novel/a-will-eternal/"));
   assert.equal(p.type, "series");
   assert.equal(p.site, "lightnovelworld");
   assert.equal(p.seriesId, "a-will-eternal");
   assert.equal(p.title, "A Will Eternal");
-  assert.equal(p.cover, "https://lightnovelworld.net/wp-content/uploads/awe.webp");
 });
 
 test("lightnovelworld.detect strips the chapter suffix off the heading", () => {
@@ -141,8 +128,6 @@ test("lightnovelworld.detect strips the chapter suffix off the heading", () => {
   assert.equal(p.chapterLabel, "Chapter 1298");
   assert.equal(p.title, "A Will Eternal");
   assert.equal(p.seriesUrl, "https://lightnovelworld.net/novel/a-will-eternal/");
-  // Chapter pages have no cover; the merge in bookmarkCurrent keeps the stored one.
-  assert.equal(p.cover, "");
 });
 
 test("lightnovelworld.detect returns other for non-series paths", () => {