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/data/ai-tools/codex.json

@@ -14,6 +14,9 @@
     "package": "@openai/codex"
   },
   "update": {
-    "kind": "npm"
+    "kind": "self",
+    "args": [
+      "update"
+    ]
   }
 }

server/data/ai-tools/hermes.json

@@ -15,5 +15,12 @@
     "--yolo"
   ],
   "homepageUrl": "https://hermes-agent.nousresearch.com/docs/",
-  "faviconDomain": "nousresearch.com"
+  "faviconDomain": "nousresearch.com",
+  "update": {
+    "kind": "self",
+    "args": [
+      "update",
+      "--yes"
+    ]
+  }
 }

server/data/ai-tools/openclaw.json

@@ -9,5 +9,12 @@
     "delayMs": 3000
   },
   "homepageUrl": "https://github.com/openclaw/openclaw",
-  "faviconDomain": "openclaw.ai"
+  "faviconDomain": "openclaw.ai",
+  "update": {
+    "kind": "self",
+    "args": [
+      "update",
+      "--yes"
+    ]
+  }
 }