feat(hub): support remote URLs in skill_md registry field

The hub previously always prepended the monorepo base URL to skill_md
values, breaking links for CLIs that moved to standalone repos. Now
absolute URLs (starting with "http") are passed through directly.

Also restores the zotero skill_md link pointing to its standalone repo.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docs/hub/index.html

@@ -1002,7 +1002,7 @@
           ? `<div class="card-requires"><strong>Requires</strong> ${esc(c.requires)}</div>`
           : '';
         const skillLink = c.skill_md
-          ? `<a href="${REPO}/blob/main/${c.skill_md}" target="_blank">Skill</a>`
+          ? `<a href="${c.skill_md.startsWith('http') ? c.skill_md : `${REPO}/blob/main/${c.skill_md}`}" target="_blank">Skill</a>`
           : '';
         const sourceLink = `<a href="${REPO}/tree/main/${c.name}/agent-harness" target="_blank">Source</a>`;
         const titleHtml = c.homepage

registry.json

@@ -196,7 +196,7 @@
       "homepage": "https://github.com/PiaoyangGuohai1/cli-anything-zotero",
       "install_cmd": "pip install cli-anything-zotero",
       "entry_point": "cli-anything-zotero",
-      "skill_md": null,
+      "skill_md": "https://github.com/PiaoyangGuohai1/cli-anything-zotero/blob/main/cli_anything/zotero/skills/SKILL.md",
       "category": "office",
       "contributor": "PiaoyangGuohai1",
       "contributor_url": "https://github.com/PiaoyangGuohai1"