**refactor(cliproxy, config): remove vertex-compat flow, streamline Vertex API key handling**

- Removed `vertex-compat` executor and related configuration.
- Consolidated Vertex compatibility checks into `vertex` handling with `apikey`-based model resolution.
- Streamlined model generation logic for Vertex API key entries.

internal/config/vertex_compat.go

@@ -55,7 +55,7 @@ func (cfg *Config) SanitizeVertexCompatKeys() {
 		}
 		entry.BaseURL = strings.TrimSpace(entry.BaseURL)
 		if entry.BaseURL == "" {
-			// BaseURL is required for vertex-compat keys
+			// BaseURL is required for Vertex API key entries
 			continue
 		}
 		entry.ProxyURL = strings.TrimSpace(entry.ProxyURL)