feat(plugin-catalog): add openrouter-voice (community, voice)

Adds the OpenRouter voice plugin: speech-to-text and text-to-speech providers for
stt.provider / tts.provider = openrouter, reusing OPENROUTER_API_KEY. Stdlib only.

Owner submission (README rule 5): the plugin repository's owner is opening this PR.
Pinned to a1b01810cdd6be15be61f2c6f6e05e24dafbba14 (rule 2) — exact 40-hex, no
branch or tag.

Policy compliance:
- rule 3 (no self-updating code): pure Python; the plugin never fetches GitHub and
  never rewrites its own distribution. Updates reach users only through
  `hermes plugins update` and a SHA-bump PR here.
- rule 6 (declared capabilities match reality): registers no tools, hooks or
  middleware; requires OPENROUTER_API_KEY, which is the only env var it reads.

Both CI gates checked locally before opening: scripts/validate_plugin_catalog.py
passes on the whole directory, and an anonymous clone at the pinned sha followed by
`hermes plugins validate` passes.

plugin-catalog/openrouter-voice.yaml

@@ -0,0 +1,15 @@
+name: openrouter-voice
+repo: https://github.com/esketids/hermes-openrouter-voice
+sha: a1b01810cdd6be15be61f2c6f6e05e24dafbba14
+description: OpenRouter speech-to-text and text-to-speech providers for Hermes Agent (stt.provider / tts.provider = openrouter).
+maintainer: esketids
+tier: community
+category: voice
+requires_hermes: ">=0.21"
+docs_url: https://github.com/esketids/hermes-openrouter-voice#readme
+capabilities:
+  provides_tools: []
+  provides_hooks: []
+  provides_middleware: []
+  requires_env:
+  - OPENROUTER_API_KEY