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/harness/tools/custom/check-required-args.ts

@@ -0,0 +1,21 @@
+type Params = {
+    /**
+     * The tool's JSON schema.
+     */
+    parameters: Record<string, unknown>;
+    args: Record<string, unknown>;
+};
+
+/**
+ * Throws when the model left out an argument the tool's schema requires.
+ * The rest of the schema is the model's to follow: custom tools fill
+ * templates, so a wrong type does no harm the call wouldn't show.
+ */
+export default function checkRequiredArgs({ parameters, args }: Params) {
+    const required = Array.isArray(parameters.required) ? parameters.required.map(String) : [];
+    const missing = required.filter((key) => args[key] === undefined || args[key] === null || args[key] === "");
+
+    if (missing.length) {
+        throw new Error(`Missing required arguments: ${missing.join(", ")}.`);
+    }
+}