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

client/src/lib/api.ts

@@ -2011,7 +2011,6 @@ export const api = {
     /** GET /api/ai-tools/job - the current or last job, or null. */
     job: () => request<AiToolJob | null>("/ai-tools/job"),
     /** GET /api/ai-tools/versions - npm version badges, cached a day server-side. */
-    versions: () => request<Record<string, AiToolVersion>>("/ai-tools/versions"),
     /** The server-cached icon; an <img> cannot send the bearer header, so the token rides the query. */
     iconUrl: (id: string) => {
       const token = dashboardToken();
@@ -3090,15 +3089,6 @@ export interface AiToolJob {
   log: string;
 }
 
-/** One row of GET /api/ai-tools/versions. */
-export interface AiToolVersion {
-  /** Its binary lives under npm's global prefix, so an npm update replaces it. */
-  npmManaged: boolean;
-  installed: string | null;
-  latest: string | null;
-  updateAvailable: boolean;
-}
-
 export interface AiRouter {
   /** Identifier, derived from the label. Stable: a lane stores this. */
   name: string;