Track `bon` crate evolution for future migration opportunities

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Background

The SDK adopted bon v3.8.2 for RestTransportBuilder and GrpcTransportBuilder (see PRD.md). Several builder patterns were intentionally not converted due to bon limitations:

• IntoFuture builders (11 total): bon generates .build() finalizers, breaking ergonomic .await syntax
• ClientBuilder typestate: bon doesn't support phantom type state transitions
• Streaming builders: bon expects single finalizer, but these have dual finalizers (.collect() + .stream())

Features to Monitor

Feature	Use Case	Monitor For
IntoFuture support	Ergonomic async API	#[builder(finish_fn = into_future, trait = "IntoFuture")]
Dual finalizers	Streaming APIs	#[builder(finish_fn = ["collect", "stream"])]
Typestate support	Compile-time requirement enforcement	Improved phantom type support

Quarterly Review Checklist

• Check bon changelog for new features
• Review bon GitHub releases
• Evaluate if any preserved builders can now be converted
• Update this issue with findings

References

• Current bon version: =3.8.2
• PRD: PRD.md in this repo
• Builder pattern guidelines: CONTRIBUTING.md

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