feat(skills): add promptfoo skill for LLM evaluation and red-teaming

Covers install, configuration, running evals, red-teaming, CI/CD
integration, and dataset generation. Pins to v0.121.17 with acquisition
notice (OpenAI, March 2026) and documented fallbacks (DeepEval, Arize Phoenix).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

plugins/kyberforge/skills/promptfoo/META.md

@@ -0,0 +1,18 @@
+```yaml
+version: "1.0"
+updated: 2026-06-21
+
+when: >
+  Invoked explicitly as /promptfoo, or implicitly when the user wants to install,
+  configure, run evaluations, red-team an LLM application, or integrate LLM testing
+  into CI/CD using Promptfoo. Also triggered when the user wants to compare model
+  outputs side-by-side across providers.
+
+references:
+  - https://promptfoo.dev/docs/getting-started
+  - https://promptfoo.dev/docs/configuration/parameters
+  - https://promptfoo.dev/docs/usage/command-line
+  - https://promptfoo.dev/docs/configuration/expected-outputs
+  - https://promptfoo.dev/docs/red-team/
+  - https://promptfoo.dev/docs/category/integrations
+```