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/pages/Settings.tsx

@@ -1,6 +1,6 @@
 /**
  * @file Settings.tsx
- * @description Settings → Dashboard: the install-wide settings — total cost, appearance, AI Tools, lanes housekeeping, import, remote sources, Sagi, notifications, alerts, data management and system information. Per-tool settings live in that tool's own tab (Claude Code's pricing, hooks and CLAUDE_HOME: `components/settings/ClaudeAgentHubSettings.tsx`).
+ * @description Settings → Dashboard: the install-wide settings — total cost, appearance, lanes housekeeping, import, remote sources, Sagi, notifications, alerts, data management and system information. Per-tool settings live in that tool's own tab (Claude Code's pricing, hooks and CLAUDE_HOME: `components/settings/ClaudeAgentHubSettings.tsx`). AI Tools is a modal opened from the tab bar (`SettingsHub.tsx`).
  * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
  */
 /* =============================================================================
@@ -60,7 +60,6 @@ import { useTranslation } from "react-i18next";
 import {
   DollarSign,
   Palette,
-  Bot,
   RefreshCw,
   Database,
   HardDrive,
@@ -112,7 +111,6 @@ import { RemoteSources } from "../components/RemoteSources";
 import { Skeleton } from "../components/Skeleton";
 import { AlertsNotifications } from "../components/AlertsNotifications";
 import { AppearanceSettings } from "../components/settings/AppearanceSettings";
-import { AiToolsSettings } from "../components/settings/AiToolsSettings";
 import type { WSMessage } from "../lib/types";
 
 // In-page navigation for the (dense) Settings screen. Each entry maps to a
@@ -124,7 +122,6 @@ const SETTINGS_SECTIONS: {
   Icon: typeof DollarSign;
 }[] = [
   { id: "appearance", labelKey: "appearance.title", Icon: Palette },
-  { id: "ai-tools", labelKey: "aiTools.title", Icon: Bot },
   { id: "lanes", labelKey: "lanesSection.title", Icon: GitBranch },
   { id: "import", labelKey: "import.title", fallback: "Import", Icon: History },
   {
@@ -626,8 +623,6 @@ export function Settings() {
 
       <AppearanceSettings />
 
-      <AiToolsSettings />
-
       {/* ─── LANES ─── */}
       <section id="lanes" className="scroll-mt-24">
         <h3 className="text-sm font-medium text-fg-secondary flex items-center gap-2 mb-1">