Rationalize config file locations and update documentation

architecture.md

@@ -94,6 +94,13 @@ Adapter behavior:
 
 ## 5. Configuration Contract
 
+CLI pipeline config path resolution:
+
+- when `--config <path>` is provided, that path is used
+- when `--config` is omitted, Narratio searches defaults in order:
+  - `/usr/local/etc/narratio/pipeline.yml`
+  - `/etc/narratio/pipeline.yml`
+
 `pipeline.scriptorium` is optional. Existing pipelines without Scriptorium continue to work.
 
 `pipeline.trim` is optional. Existing pipelines without trim config continue to work.