feat(skills): import SKILL.md bundles from public GitHub URLs (#2576)

* feat(skills): import SKILL.md bundles from public GitHub URLs

Supports GitHub tree/blob/raw links and skills.sh pages that resolve to GitHub.
Installs SKILL.md plus sibling text assets under data/skills/imported/.

Co-authored-by: Cursor <cursoragent@cursor.com>

* fix(skills): admin-gate URL import and validate redirect hosts

- require_admin on POST /api/skills/import-from-url (matches other skill admin routes)
- reject cross-host redirects after httpx follow_redirects
- test for redirect host validation

Co-authored-by: Cursor <cursoragent@cursor.com>

* fix(skills): match Brain Add panel import/submit button styles

- Skill URL Import: theme-io-btn + download icon (same as memory Import)
- Add Skill submit: confirm-btn confirm-btn-primary

Co-authored-by: Cursor <cursoragent@cursor.com>

* fix(skills): allow api.github.com during directory import

Real imports hit the GitHub contents API after redirects; whitelist
api.github.com and add regression tests. Shrink Import button with flex:none.

Co-authored-by: Cursor <cursoragent@cursor.com>

* fix(skills): align skill Import button with URL input row

Match memory-add-input height (28px) in memory-add-row and center the
download icon with flexbox instead of vertical-align hacks.

Co-authored-by: Cursor <cursoragent@cursor.com>

* fix(skills): cancel modal-body margin on skill Import button

The skill Import button sits in .memory-add-row beside an input; the
global .modal-body button { margin-top: 6px } rule only affected buttons,
pushing Import down and misaligning the download icon. Reset margin-top
and match Memory Import SVG markup at 28px row height.

Co-authored-by: Cursor <cursoragent@cursor.com>

* fix(skills): surface GitHub API errors on URL import

Pass through GitHub response messages (especially 403 rate limits) as
SkillImportError instead of a generic download failure.

Co-authored-by: Cursor <cursoragent@cursor.com>

---------

Co-authored-by: Cursor <cursoragent@cursor.com>

static/js/skills.js

@@ -1818,6 +1818,35 @@ async function _showSkillSource(name) {
   });
 }
 
+async function importSkillFromUrl() {
+  const input = document.getElementById('skill-import-url');
+  const url = (input?.value || '').trim();
+  if (!url) {
+    uiModule.showError('Paste a GitHub or skills.sh URL first');
+    return;
+  }
+  const btn = document.getElementById('skill-import-url-btn');
+  if (btn) btn.disabled = true;
+  try {
+    const res = await fetch(`${API}/api/skills/import-from-url`, {
+      method: 'POST',
+      headers: { 'Content-Type': 'application/json' },
+      body: JSON.stringify({ url }),
+    });
+    const data = await res.json().catch(() => ({}));
+    if (!res.ok) throw new Error(data.detail || data.error || `HTTP ${res.status}`);
+    if (input) input.value = '';
+    await loadSkills();
+    const name = data.skill?.name || 'skill';
+    uiModule.showToast(`Imported ${name} (${data.files || 1} file(s))`);
+    if (name) openSkill(name);
+  } catch (err) {
+    uiModule.showError('Import failed: ' + err.message);
+  } finally {
+    if (btn) btn.disabled = false;
+  }
+}
+
 async function addSkill() {
   const name = document.getElementById('new-skill-name')?.value.trim()
     || document.getElementById('new-skill-title')?.value.trim();
@@ -1866,6 +1895,10 @@ async function addSkill() {
 }
 
 document.addEventListener('DOMContentLoaded', () => {
+  document.getElementById('skill-import-url-btn')?.addEventListener('click', importSkillFromUrl);
+  document.getElementById('skill-import-url')?.addEventListener('keydown', (e) => {
+    if (e.key === 'Enter') importSkillFromUrl();
+  });
   document.getElementById('add-skill-btn')?.addEventListener('click', addSkill);
   document.getElementById('skills-search')?.addEventListener('input', renderSkillsList);
   document.getElementById('skills-sort')?.addEventListener('change', (e) => {