feat(server): migrate copilot to native (#14620)

#### PR Dependency Tree


* **PR #14620** 👈

This tree was auto-generated by
[Charcoal](https://github.com/danerwilliams/charcoal)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **New Features**
* Native LLM workflows: structured outputs, embeddings, and reranking
plus richer multimodal attachments (images, audio, files) and improved
remote-attachment inlining.

* **Refactor**
* Tooling API unified behind a local tool-definition helper;
provider/adapters reorganized to route through native dispatch paths.

* **Chores**
* Dependency updates, removed legacy Google SDK integrations, and
increased front memory allocation.

* **Tests**
* Expanded end-to-end and streaming tests exercising native provider
flows, attachments, and rerank/structured scenarios.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/backend/native/Cargo.toml

@@ -21,7 +21,10 @@ image = { workspace = true }
 infer = { workspace = true }
 libwebp-sys = { workspace = true }
 little_exif = { workspace = true }
-llm_adapter = { workspace = true }
+llm_adapter = { workspace = true, default-features = false, features = [
+  "ureq-client",
+] }
+matroska = { workspace = true }
 mp4parse = { workspace = true }
 napi = { workspace = true, features = ["async"] }
 napi-derive = { workspace = true }