feat(provider): add Nous Research as first-class provider

[Aboozle1]

Fixes #7525

Adds Nous Research as a first-class provider using their inference API.

Changes:

• Add provider definition with 7 models (Hermes 4.3, Hermes 4, DeepHermes 3, Hermes 3)
• Support NOUS_API_KEY env var and /connect auth
• Add documentation to providers.mdx

Testing:

• /connect → searched "nous" → entered API key
• /models → verified 7 models appear
• Tested prompt with all models