feat: configure GonkaGate as named Hermes provider

[Dankosik]

Summary

• switch the helper-managed Hermes config to providers.gonkagate for latest Hermes picker compatibility
• write model.provider = gonkagate and populate provider models from the qualified-live intersection
• set discover_models: false so Hermes keeps the curated qualified model subset instead of replacing it with the full live catalog
• migrate the old direct custom config and previous custom_providers[name=gonkagate] shape, and update conflict handling, docs, launch qualification artifacts, and mirrored skills

Verification

• npm run ci
• git diff --check