Add MCP servers and custom tools for bots

Two new settings pages, MCPs and Tools. Super admins define them; super
admins and admins attach them to bots, to workspaces (every bot there),
or to every bot. Bots get them in chat replies and tasks.

- Custom tools: a JSON-schema of arguments plus an HTTP request, a script
  on the bot's computer, or a prompt, templated with {{args.x}} and
  {{env.KEY}}, secrets redacted from results.
- MCP servers: remote (URL and headers) or stdio commands run on the host
  with a setup command and an isolated env, in a per-process pool. Tools
  are listed into a cache and connect on first call.
- Add, edit, access and try open in modals.
- Markdown, JSON and command fields use twui's AceEditor (CodeEditor),
  its scripts loaded on demand.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/utils/mcp-server-slug.ts

@@ -0,0 +1,18 @@
+type Params = {
+    name: string;
+};
+
+/**
+ * A server's slug from its name: lowercase letters, numbers and single
+ * underscores, at most 24 characters, so its tools' names stay short.
+ */
+export default function mcpServerSlug({ name }: Params) {
+    const slug = name
+        .toLowerCase()
+        .replace(/[^a-z0-9]+/g, "_")
+        .replace(/^_+|_+$/g, "")
+        .slice(0, 24)
+        .replace(/_+$/g, "");
+
+    return slug || "mcp";
+}