feat: adapt cloudflare worker ai (#14732)

#### PR Dependency Tree


* **PR #14732** 👈

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**
* Cloudflare Workers AI added as a Copilot provider (configurable in
admin settings).
  * Gemini 3.1 Flash Lite Preview model made available.

* **Behavior Changes**
* Reranking now uses a different default model identifier (affects
relevancy scores).

* **Tests**
* Rerank tests adjusted to focus on the updated model and expected
results.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Cargo.lock

@@ -3371,9 +3371,9 @@ dependencies = [
 
 [[package]]
 name = "llm_adapter"
-version = "0.1.3"
+version = "0.1.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e98485dda5180cc89b993a001688bed93307be6bd8fedcde445b69bbca4f554d"
+checksum = "cd95a9dd20745f3d80d47460e6cf6131921bef928c38fcd961b10b574d749305"
 dependencies = [
  "base64",
  "serde",