Fix MCP env var check skipped when any gateway preflight errors

When GatherEnvVarsForTools returned a preflight error for any MCP
toolset, the successfully-gathered env var names from other toolsets
were silently discarded because they were only processed in the else
branch. This meant configs with multiple MCP refs (where at least one
gateway call failed) would bypass all tool env var validation.

Assisted-By: docker-agent

Author: dgageot

pkg/config/gather.go

@@ -33,10 +33,12 @@ func gatherMissingEnvVars(ctx context.Context, cfg *latest.Config, modelsGateway
 	if err != nil {
 		// Store tool preflight error but continue checking models
 		toolErr = err
-	} else {
-		for _, e := range names {
-			requiredEnv[e] = true
-		}
+	}
+	// Always add tool env vars, even when some toolsets had preflight errors.
+	// Previously, a preflight error from one toolset would cause all tool
+	// env vars to be silently skipped.
+	for _, e := range names {
+		requiredEnv[e] = true
 	}
 
 	for _, e := range sortedKeys(requiredEnv) {