fix(config): delete the model-routing chain — nothing has called it since April (#119)

Closes #116.

Deletes config/models.yaml, internal/config/models.go (LoadModels, ModelFor),
its test, the ModelsFile field on Config, and SUPERVISOR_MODELS_FILE from
.env.example. Option A from the issue.

Merge-gate evidence: negative claim independently re-established (no Go, shell,
Dockerfile, k8s, CI or infra-repo caller); task check exit 0 across both
modules; CI run 7374 green on the PR head.

Co-authored-by: Mathias <mthbqv@gmail.com>

internal/config/config.go

@@ -7,7 +7,6 @@ type Config struct {
 	LiteLLMBaseURL string // LITELLM_BASE_URL, default http://iguana:4000
 	LiteLLMAPIKey  string // LITELLM_API_KEY
 	ConfigDir      string // SUPERVISOR_CONFIG_DIR, default ./config/supervisor
-	ModelsFile     string // SUPERVISOR_MODELS_FILE, default <ConfigDir>/../models.yaml
 	IngestBaseURL  string // INGEST_BASE_URL, default http://localhost:3300
 	IngestSvcURL   string // INGEST_SVC_URL — base URL for brain_ingest (/ingest, /ingest-path)
 	KBRetrievalURL string // KB_RETRIEVAL_URL — base URL for brain_search
@@ -23,7 +22,6 @@ func Load() (Config, error) {
 		LiteLLMAPIKey:  os.Getenv("LITELLM_API_KEY"),
 		ConfigDir:      envOr("SUPERVISOR_CONFIG_DIR", "./config/supervisor"),
 	}
-	cfg.ModelsFile = envOr("SUPERVISOR_MODELS_FILE", cfg.ConfigDir+"/../models.yaml")
 	cfg.IngestBaseURL = envOr("INGEST_BASE_URL", "http://localhost:3300")
 	cfg.IngestSvcURL = envOr("INGEST_SVC_URL", "")
 	cfg.KBRetrievalURL = envOr("KB_RETRIEVAL_URL", "")