fix(catalog): point seed entry at a real plugin subdir

The example-plugins repo is a multi-plugin repo with no root plugin.yaml;
the admission CI correctly rejected the root-level seed entry. Pin the
plugin-llm-example subdir instead — the admission gate catching its own
seed entry is the E2E proof it works.

plugin-catalog/plugin-llm-example.yaml

@@ -1,8 +1,8 @@
-name: example-plugin
+name: plugin-llm-example
 repo: https://github.com/NousResearch/hermes-example-plugins
 sha: 38fe0fb53eff98d477f807432e965429e665ca33
-subdir: ""
+subdir: "plugin-llm-example"
-description: Reference example plugins for the Hermes plugin system.
+description: Reference plugin showing host-owned structured LLM access via ctx.llm.
 maintainer: NousResearch
 tier: official
 docs_url: ""