feat(kenari): add new provider

[doedja]

What

Adds Kenari, an Indonesian LLM gateway with an OpenAI-compatible API, as a provider.

• internal/providers/configs/kenari.json: 31 chat models (all support tool calling and streaming), generated from the live catalog at GET https://kenari.id/v1/models (public, no auth)
• Registered in internal/providers/providers.go (alphabetical slot)

Details

• type: openai-compat, endpoint https://kenari.id/v1, key env $KENARI_API_KEY
• Costs are set to 0 like copilot and kimi-coding: Kenari bills a local-currency (IDR) wallet per token, so there is no stable USD per-token price to pin. Live pricing is on the models endpoint and https://kenari.id/models
• context_window, can_reason, reasoning_levels, and supports_attachments come from the same models endpoint
• Free-tier model variants (:free ids) are excluded, only the stable paid catalog is listed
• Defaults: claude-sonnet-5 (large) / deepseek-v4-flash (small)

Testing

• go build ./... and go test ./... pass (41 tests, 22 packages)
• gofmt clean

Docs: https://kenari.id/docs