fix(llm): send the provider model id on the wire, not the alias

LlmManager keys its model registry by llm_models.name (the user-facing
alias), and the kernel sent ModelHandle.id as the request's model field —
so the alias, not llm_models.model_id, went on the wire. A model worked
only while the alias was left equal to the model id; renaming it made
every provider reject the call (DeepInfra 404 model_not_found, DeepSeek
400 invalid_request_error).

ModelHandle gains an optional wire_id: the model identifier to put on the
wire when the selector's id is a bookkeeping key. The kernel and the
compaction summary call both send handle.wire_model(); SkaldSelector sets
wire_id from LlmEntry.model (llm_models.model_id). Everything else keeps
keying on the alias: the chat's model pin, health reporting, fallback
exclusion and request logging are untouched.

crates/agent-loop/src/kernel.rs

@@ -149,7 +149,7 @@ pub(crate) async fn run(
             let req = ModelRequest {
                 messages: messages.clone(),
                 tools: defs.clone(),
-                model: handle.id.clone(),
+                model: handle.wire_model().to_string(),
                 max_tokens: None,
                 temperature: None,
                 request_id: mint_request_id(),