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/i18n/locales/en/settings.json

@@ -530,9 +530,7 @@
     "homepageOf": "{{tool}} homepage",
     "install": "Install",
     "update": "Update",
-    "updateTools": "Update tools",
-    "newVersion": "v{{version}} available",
-    "outsideNpm": "Installed outside npm — update it the way you installed it",
+    "updateAll": "Update all ({{count}})",
     "runScript": "Download {{url}} and run it with bash",
     "confirmInstall": "Install {{tool}}?",
     "confirmUpdate": "Update {{tool}}?",
@@ -542,7 +540,9 @@
     "cancel": "Cancel",
     "jobRunning": "Running…",
     "jobOk": "Done",
-    "jobFailed": "Failed (exit {{code}})"
+    "jobFailed": "Failed (exit {{code}})",
+    "showLog": "Show log",
+    "hideLog": "Hide log"
   },
   "appearance": {
     "title": "Appearance",