fix(doctor): skip /models health check for providers that don't support it

[jak983464779]

Problem

Xiaomi MiMo's /v1/models endpoint returns 401 even with a valid API key, causing hermes doctor to falsely report "invalid API key".

This isn't unique to Xiaomi — any provider whose /models endpoint doesn't support auth verification will trigger the same false positive.

Solution

3 files, 4 lines added:

1. providers/base.py — Add supports_health_check: bool = True field to ProviderProfile. Providers that don't support /models for auth verification can set it to False.

2. hermes_cli/doctor.py — Dynamic provider discovery now reads supports_health_check from the profile instead of hardcoding True.

3. plugins/model-providers/xiaomi/__init__.py — Set supports_health_check=False for Xiaomi MiMo.

Before and After

# Before
✗ xiaomi               (invalid API key)
Found 2 issue(s) to address

# After  
✓ xiaomi               (key configured)
Found 1 issue(s) to address

Testing

• Verified hermes doctor no longer reports false positive for Xiaomi
• Existing providers with supports_health_check=True (default) are unaffected

[teknium1]

Merged via PR #24657 (cherry-picked onto current main with your authorship preserved). Thanks for the contribution!