feat(server): converge legacy compatibility (#15426)

#### PR Dependency Tree


* **PR #15426** 👈

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**
* Added workspace BYOK profiles with provider/model catalogs, capability
validation, connection probing, credential rotation, reordering, and
secure local leases.
* Added Copilot route options, selectable targets, managed tiers,
explicit profile/model overrides, and improved streaming with tool
callbacks and abort support.
* Added Copilot availability controls to prevent access when the feature
is disabled.
* **Changes**
* Simplified Copilot configuration and removed legacy provider-specific
settings.
* Removed obsolete model, token-cost, transcript strategy, and provider
metadata fields from public responses.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/backend/native/src/llm/route/contract.rs

@@ -0,0 +1,50 @@
+#[napi_derive::napi(string_enum)]
+#[derive(Clone, Copy, PartialEq, Eq)]
+pub enum CopilotManagedTier {
+  Standard,
+  Premium,
+}
+
+#[derive(Clone)]
+#[napi_derive::napi(object)]
+pub struct CopilotAccessProjection {
+  pub route_allowed: bool,
+  pub managed_tier: CopilotManagedTier,
+  pub server_byok: bool,
+  pub local_byok: bool,
+}
+
+#[derive(Clone)]
+#[napi_derive::napi(object)]
+pub struct CopilotTargetOverrideInput {
+  pub profile_id: String,
+  pub model_id: String,
+}
+
+#[derive(Clone)]
+#[napi_derive::napi(object)]
+pub struct CopilotRouteCheckInput {
+  pub slot: String,
+  pub built_in_route_id: Option<String>,
+  pub workspace_id: Option<String>,
+  pub user_id: Option<String>,
+  pub local_lease_id: Option<String>,
+  pub access: CopilotAccessProjection,
+  pub managed_target_id: Option<String>,
+  pub target_override: Option<CopilotTargetOverrideInput>,
+}
+
+#[derive(Clone)]
+#[napi_derive::napi(object)]
+pub struct CopilotExecuteInput {
+  pub slot: String,
+  pub built_in_route_id: Option<String>,
+  pub workspace_id: Option<String>,
+  pub user_id: Option<String>,
+  pub local_lease_id: Option<String>,
+  pub access: CopilotAccessProjection,
+  pub managed_target_id: Option<String>,
+  pub target_override: Option<CopilotTargetOverrideInput>,
+  #[napi(ts_type = "unknown")]
+  pub request: serde_json::Value,
+}