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/dict/private-tables.ts

@@ -2,7 +2,7 @@ import type { TableType } from "@/src/types";
 
 /**
  * Tables holding secrets (password hashes, pending login codes, model
- * provider keys, envs). They are never reachable through the admin CRUD API, not
+ * provider keys, envs, MCP servers' headers and env). They are never reachable through the admin CRUD API, not
  * even by super admins.
  */
 export const PrivateTables: TableType[] = [
@@ -10,4 +10,5 @@ export const PrivateTables: TableType[] = [
     "sso_login_codes",
     "harness_providers",
     "envs",
+    "mcp_servers",
 ];