Read skills from the global and workspace .agents/skills directories

- Discover skill directories under ~/.agents/skills and each
  workspace''s .agents/skills; a directory qualifies with a full
  skill.manifest.json or just a SKILL.md, whose manifest is derived
  (frontmatter name or the directory name). Paths resolve per platform
  on Windows, macOS, and Linux.
- Sync at startup for every organization and again when the Skills
  page opens; skills the org already carries are skipped, and one
  broken directory cannot block the rest.
- AGENTCOMPANY_NEW_SKILLS_ROOT points tests at a temporary library
  (overriding USERPROFILE crashes Electron on Windows).

src/renderer/src/pages/settings/SkillsPanel.tsx

@@ -1,4 +1,4 @@
-import { useState, type FormEvent } from "react";
+import { useEffect, useState, type FormEvent } from "react";
 import { Button, Field, Icon, Pill } from "../../shared/ui";
 import { Dialog } from "../../shared/Dialog";
 import type {
@@ -23,6 +23,12 @@ interface SkillsPanelProps {
 export function SkillsPanel({ orgId, skills, revisions, bindings, tests, agents, actions }: SkillsPanelProps) {
   const [importOpen, setImportOpen] = useState(false);
 
+  // The on-disk skill library (global ~/.agents/skills and each workspace's
+  // .agents/skills) syncs in when the panel opens.
+  useEffect(() => {
+    void actions.run(() => window.agentCompany.syncSkillsFromDisk({ orgId }));
+  }, [orgId, actions]);
+
   const importSkill = (event: FormEvent<HTMLFormElement>) => {
     event.preventDefault();
     const form = new FormData(event.currentTarget);