fix(qwen): gadfly round 3 — stop guarding a duplicate, delete it

Twelve findings, all real, and the two that matter are about the pre-flight I
added rather than about qwen.

The credential check had a false pass in the OTHER direction from round 2's: on
the GADFLY_BASE_URL override path, resolveModel builds the client with
GADFLY_API_KEY and never reads QWEN_API_KEY/KIMI_API_KEY, so treating the
provider's own key as sufficient there let a doomed run proceed. Having now
been wrong about these rules in both directions, the check no longer tries to
model both paths: it covers the REGISTRY path, whose rules it can state
exactly, and says nothing about the override path — which is hand-configured by
definition, while the registry path is the one you hit by adding a model id to
a var and forgetting the secret.

The logic moves to scripts/preflight.sh, sourced by both run.sh and the test.
The previous answer to "this test duplicates production logic" was a regex
drift-guard, and that guard compared only the provider table — not the decision
logic, which is precisely the half that carried the bug. A duplicate you guard
is still a duplicate; this deletes it, and the test now runs under `set -u`
like production does.

Also: the test that pins the shared provider slice held its own copy of the
list (now ranges the slice); endpointProviderNames had nothing tying it to the
switches it describes, which is how it shipped without "gemini" (a new test
asserts every advertised name resolves); two godoc lists had drifted; and the
"sanity" line that asserted nothing is gone.

And the repo had NO test job — `go test` and the pre-flight table both existed
and neither was ever executed by CI, which reads as coverage while providing
none. Added one (build/vet/gofmt/test/pre-flight), running alongside the image
build rather than gating it, so red is loud without standing between a push and
a rebuild.

Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>

cmd/gadfly/model_test.go

@@ -1,6 +1,9 @@
 package main
 
-import "testing"
+import (
+	"strings"
+	"testing"
+)
 
 func TestEndpointProvider(t *testing.T) {
 	t.Run("ollama http endpoint registers under its name", func(t *testing.T) {
@@ -77,7 +80,9 @@ func TestEndpointProvider(t *testing.T) {
 // reason a user could guess — which is exactly what happened here on the first
 // pass. Asserting both in one table is what makes the pair fail together.
 func TestOpenAICompatProvidersResolveOnBothPaths(t *testing.T) {
-	for _, provider := range []string{"openai", "openai-compatible", "kimi", "qwen"} {
+	// Ranges the SHARED slice rather than a fourth copy of the names: a test
+	// that pins a list against drift must not be able to drift from it.
+	for _, provider := range openAICompatProviders {
 		t.Run(provider+" via GADFLY_ENDPOINT_*", func(t *testing.T) {
 			p, err := endpointProvider("ep", provider+"|https://host.example/v1|sk-x")
 			if err != nil {
@@ -99,6 +104,25 @@ func TestOpenAICompatProvidersResolveOnBothPaths(t *testing.T) {
 	}
 }
 
+// TestEndpointProviderNamesAreAllAccepted keeps the operator-facing list
+// honest. endpointProviderNames exists to stop two error messages drifting
+// apart, but nothing tied it to the switches it describes — and its first
+// version had already dropped the "gemini" alias, so the anti-drift list was
+// itself drifted. Every name it advertises must actually resolve.
+func TestEndpointProviderNamesAreAllAccepted(t *testing.T) {
+	for _, name := range strings.Split(endpointProviderNames, "/") {
+		name = strings.TrimSpace(name)
+		if name == "" {
+			continue
+		}
+		t.Run(name, func(t *testing.T) {
+			if _, err := endpointProvider("ep", name+"|https://host.example/v1|sk-x"); err != nil {
+				t.Errorf("endpointProviderNames advertises %q but endpointProvider rejects it: %v", name, err)
+			}
+		})
+	}
+}
+
 func TestBuildSpec(t *testing.T) {
 	tests := []struct {
 		name     string