fix: add evals/promptfoo as workspace member for Deno compatibility

Deno requires all package.json files under the workspace root to be
listed as workspace members, even if excluded from lint/fmt/test.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: stack72

deno.json

@@ -3,7 +3,7 @@
   "version": "0.1.0",
   "license": "AGPL-3.0-only",
   "exports": "./main.ts",
-  "workspace": ["packages/client", "packages/testing"],
+  "workspace": ["packages/client", "packages/testing", "evals/promptfoo"],
   "tasks": {
     "dev": "deno run --unstable-bundle --allow-read --allow-write --allow-env --allow-run --allow-sys main.ts",
     "test": "deno test --unstable-bundle --allow-read --allow-write --allow-env --allow-run --allow-net --allow-sys",