feat(ui): AI Tools modal, one-button lane tool picker, AgentHub settings in Overview, markdown preview

- AI Tools moves from a Settings section into a modal behind a button at the
  Settings tab bar's right edge (AiToolsModal, `actions` on PageTabs,
  /settings#ai-tools); rows get an enable switch, Default badge, and an
  Update button for every tool whose catalog names an updater (no version
  lookup on open); not-installed tools fold behind a disclosure, a finished
  job's log folds to one line; shared AiToolIcon
- codex updates through its own `codex update`, openclaw/hermes gain
  `update --yes`; update-all runs every installed updater and skips an npm
  one only when npm does not manage the binary
- Add-lane tool picker is one button showing the chosen tool that opens the
  enabled tools as buttons
- Claude Code / Codex AgentHub sub-tab folded into Overview (home editor,
  hooks, pricing); the path list drops CLAUDE_HOME/CODEX_HOME;
  HomeDirSetting shows the saved value only while the field differs
- Preview/Raw toggle for markdown files in the config FileViewer and the
  Changes panel's whole-file view (MarkdownPreview: react-markdown +
  remark-gfm, raw HTML never run, frontmatter as a code block)
- docs and the CLAUDE.md marker updated

server/lib/ai-tool-jobs.js

@@ -247,17 +247,19 @@ async function start(id, action) {
   return view(j);
 }
 
-/** One job that updates every npm-managed tool with a newer version and every self-updater. */
+/**
+ * One job that runs every installed tool's updater — its own, or npm's when
+ * npm manages it (one installed another way is skipped). No version lookup:
+ * each updater knows whether it has anything to do.
+ */
 async function startUpdateAll() {
   claim();
   let steps = [];
   try {
-    const v = await versions.versions();
     for (const t of aiTools.list()) {
       if (!aiTools.detect(t.id).installed || !t.update) continue;
-      if (t.update.kind === "self" || (t.update.kind === "npm" && v[t.id]?.updateAvailable)) {
-        steps.push(...(await stepsFor(t.id, "update")));
-      }
+      if (t.update.kind === "npm" && !(await versions.npmManaged(t.id))) continue;
+      steps.push(...(await stepsFor(t.id, "update")));
     }
     if (!steps.length) throw makeErr("ENOTHING", "no AI tool has an update to run");
   } finally {