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/fill-template.test.ts

@@ -0,0 +1,42 @@
+import { describe, expect, test } from "bun:test";
+import fillTemplate from "./fill-template";
+
+describe("fillTemplate", () => {
+    test("fills args and envs", () => {
+        expect(
+            fillTemplate({
+                template: "https://api.test/{{args.city}}?key={{ env.API_KEY }}",
+                args: { city: "Lagos" },
+                envs: [{ key: "API_KEY", value: "abc" }],
+            }),
+        ).toBe("https://api.test/Lagos?key=abc");
+    });
+
+    test("objects become JSON, missing args empty, dotted paths reach in", () => {
+        expect(
+            fillTemplate({
+                template: "{{args.filter}}|{{args.missing}}|{{args.filter.tag}}",
+                args: { filter: { tag: "x" } },
+            }),
+        ).toBe('{"tag":"x"}||x');
+    });
+
+    test("encodes filled arguments only", () => {
+        expect(
+            fillTemplate({
+                template: "{{env.BASE}}/q?s={{args.q}}&x=a b",
+                args: { q: "a b&c" },
+                envs: [{ key: "BASE", value: "https://x.test/v1" }],
+                encode: encodeURIComponent,
+            }),
+        ).toBe("https://x.test/v1/q?s=a%20b%26c&x=a b");
+    });
+
+    test("an unset env throws, naming it", () => {
+        expect(() => fillTemplate({ template: "{{env.NOPE}}" })).toThrow("NOPE");
+    });
+
+    test("leaves other braces alone", () => {
+        expect(fillTemplate({ template: '{"a": "{{other}}"}' })).toBe('{"a": "{{other}}"}');
+    });
+});