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

README.md

@@ -225,7 +225,7 @@ Codex lane's run panel offers Codex's own sandbox, approval and reasoning-effort
 choices, and resumes with `codex resume --last`. Codex sessions and token usage
 are read from Codex's own rollout journals: every Codex session (a lane's or
 not) appears in Sessions with a **Codex** badge and is priced like any other,
-with OpenAI rates filled in automatically (Settings → Codex → AgentHub). For a
+with OpenAI rates filled in automatically (Settings → Codex → Overview). For a
 live feed, install **Codex hooks** from the same tab: the next time Codex starts
 it asks you to trust them (**Trust all and continue**), and from then on each
 tool call lands in the session's timeline, a codex lane turns running/idle as