`H` in `Client<Ext, H>` refers to the HTTP backend, and not the `ApiKey`

"
The Client Struct
At the core is rig::client::Client, a generic struct parameterized by:

Ext: A provider extension (implementing the Provider trait) that defines provider-specific behavior
H: An API key type (implementing the ApiKey trait)
"

When I was going through the docs and trying out rig side by side, I noticed that H is actually defaulting to `reqwest::Client` and not related to the API Key. The documentation should be updated to reflect this

the link for reference https://rig.rs/docs/concepts/provider_clients#the-client-struct

The issue points to a specific documentation page about the Client struct. Locate the file for that page in the rig-docs repository, likely under docs/concepts/provider_clients.mdx or similar. Find the section describing the generic parameters and correct the explanation of H from 'API key type' to 'HTTP backend (defaulting to reqwest::Client)'. Verify by checking the actual Rust code in the rig framework if needed, then update the documentation accordingly.

索引モデルが issue の本文から書いたものです。