Label eval runs with the model the server actually loaded (#379)

The phrasing eval printed "llm (0.8B, ...)" no matter which gguf
llama-server had loaded, so two runs of two different models came out
named the same and were easy to mix up when comparing.

It now asks llama-server over /v1/models, same as the router eval
already did. The helper moved to internal/llm so both share it, and it
now errors instead of returning a blank name when the id field is
missing — an unreachable server gets labelled "unknown-model", never a
plausible-looking guess.

Both eval paths stay opt-in behind MAVEN_LLM_URL; no server needed for
go test.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CGeSZxh1DCtRxmFVSYVGvJ

internal/router/eval/llmrouter_test.go

@@ -61,12 +61,12 @@ func TestLLMRouterBaseline(t *testing.T) {
 	}
 
 	ctx := context.Background()
-	model, err := ModelID(ctx, base)
+	model, err := llm.ModelID(ctx, base)
 	if err != nil {
 		// Not fatal: an unlabelled score is still a score. But say so loudly,
 		// because an unlabelled row in a bake-off table is worthless.
-		t.Logf("could not read model id from %s: %v — reports will say %q", base, err, "unknown-model")
-		model = "unknown-model"
+		t.Logf("could not read model id from %s: %v — reports will say %q", base, err, llm.UnknownModel)
+		model = llm.UnknownModel
 	}
 	t.Logf("scoring model %s at %s", model, base)
 	lr := router.NewLLMRouter(client)

internal/router/eval/modelid.go

@@ -1,51 +0,0 @@
-package eval
-
-import (
-	"context"
-	"encoding/json"
-	"fmt"
-	"net/http"
-	"strings"
-)
-
-// ModelID asks llama-server which model it has loaded, so a scoring run can
-// label itself. Without this a bake-off between two models produces two tables
-// that look identical, and the operator has to remember which server was up.
-//
-// Read from the server rather than passed in on purpose: a hand-typed label
-// goes stale the moment someone restarts the server with a different -m.
-func ModelID(ctx context.Context, base string) (string, error) {
-	req, err := http.NewRequestWithContext(ctx, "GET", strings.TrimSuffix(base, "/")+"/v1/models", nil)
-	if err != nil {
-		return "", err
-	}
-	resp, err := http.DefaultClient.Do(req)
-	if err != nil {
-		return "", err
-	}
-	defer resp.Body.Close()
-	if resp.StatusCode != 200 {
-		return "", fmt.Errorf("models: status %d", resp.StatusCode)
-	}
-	var out struct {
-		Data []struct {
-			ID string `json:"id"`
-		} `json:"data"`
-	}
-	if err := json.NewDecoder(resp.Body).Decode(&out); err != nil {
-		return "", err
-	}
-	if len(out.Data) == 0 {
-		return "", fmt.Errorf("models: empty list")
-	}
-	return shortModelID(out.Data[0].ID), nil
-}
-
-// shortModelID trims the path and the .gguf suffix — llama-server reports the
-// file name it was started with, which is too long for a table header.
-func shortModelID(id string) string {
-	if i := strings.LastIndexAny(id, "/\\"); i >= 0 {
-		id = id[i+1:]
-	}
-	return strings.TrimSuffix(id, ".gguf")
-}