Replace trait with enum in Rust

[nenad1002]

Async methods on traits require [Pin<Box>] return types, which pollute the public API.

Additionally, C# interfaces and Rust traits are not equivalent abstractions, and traits offer no obvious advantage here.

Since the set of implementors is closed and internal, an enum with private variants provides the same polymorphism with a cleaner, more idiomatic Rust API.

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Project	Deployment	Actions	Updated (UTC)
foundry-local	Ready	Preview, Comment	Apr 1, 2026 8:59pm

[Copilot]

Pull request overview

This PR refactors the Rust SDK’s model abstraction by removing the public IModel trait and replacing it with a single public Model type backed by an internal enum, avoiding boxed-future trait method signatures and simplifying the public API surface.

Changes:

• Removed the public IModel trait and updated the crate exports accordingly.
• Reworked Model to wrap either a single variant or a grouped multi-variant model via an internal ModelKind enum, exposing async methods directly on Model.
• Updated Catalog, examples, samples, and integration tests to use Arc<Model> and the new download progress callback shape.

Reviewed changes

Copilot reviewed 17 out of 17 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
sdk/rust/tests/integration/model_test.rs	Updates tests to work with Arc<Model> and the new API.
sdk/rust/src/lib.rs	Stops exporting IModel / removes imodel module wiring; keeps Model as the public type.
sdk/rust/src/imodel.rs	Deletes the public IModel trait entirely.
sdk/rust/src/detail/model.rs	Introduces public Model with internal ModelKind enum and async methods on the concrete type.
sdk/rust/src/detail/model_variant.rs	Converts variant operations to concrete async methods (no trait impl) and updates docs.
sdk/rust/src/catalog.rs	Updates catalog lookups/collections to return Arc<Model> (models and per-id variants).
sdk/rust/examples/tool_calling.rs	Updates progress callback usage for download.
sdk/rust/examples/interactive_chat.rs	Updates progress callback usage for download.
sdk/rust/examples/chat_completion.rs	Updates progress callback usage for download.
samples/rust/tutorial-voice-to-text/src/main.rs	Updates progress callback usage for download.
samples/rust/tutorial-tool-calling/src/main.rs	Updates progress callback usage for download.
samples/rust/tutorial-document-summarizer/src/main.rs	Updates progress callback usage for download.
samples/rust/tutorial-chat-assistant/src/main.rs	Updates progress callback usage for download.
samples/rust/tool-calling-foundry-local/src/main.rs	Updates progress callback usage for download.
samples/rust/native-chat-completions/src/main.rs	Updates progress callback usage for download.
samples/rust/foundry-local-webserver/src/main.rs	Updates progress callback usage for download (incl. move closure).
samples/rust/audio-transcription-example/src/main.rs	Updates progress callback usage for download.

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