Default ATVM automation commands to gold config files

Stop defaulting to cypress.atvm-config.ts in ATVM guidance.

Prefer gold-named config files unless explicitly told otherwise.

Update automation examples to use cypress.atvm-config-gold.ts.

Record the run learning explaining why the old default is unreliable.

atvm/atvm-automation-guide.md

@@ -45,6 +45,8 @@ Typical sequence:
 - `cypress.atvm-config-gold.ts` -> Gold Disk 1
 - `cypress.atvm-config-gold-2.ts` -> Gold Disk 2
 - Additional numbered config variants map to corresponding Gold Disks.
+- Do not default to `cypress.atvm-config.ts`.
+- Unless the operator explicitly requests another config, use a config file with `gold` in the filename.
 
 ## Available Templates
 - `cmc-e2e`
@@ -121,6 +123,7 @@ Before any new automation request:
 When asked for one VM or a VM set:
 - choose requested template/options,
 - choose correct config file for intended Gold Disk,
+- default to a config filename containing `gold` unless the operator explicitly says otherwise,
 - use a descriptive `--build_name` without Gold Disk IDs.
 
 ## Update Rule