Scrub tracked secrets and switch ATVM docs to local credential references

- remove hardcoded credentials, tokens, registration codes, and similar secret values from tracked ATVM and CDS MCP docs
- replace those values with references to /home/aw/code/cds/.env.credentials.local and the corresponding environment variable names
- update current operator guides to instruct sourcing .env.credentials.local before credential-dependent setup and automation workflows
- update the ATVM setup scripts to consume ATVM_TARGET_PASSWORD from the environment instead of hardcoding the Ubuntu root SSH password
- scrub the remaining tracked artifact log entry that still included the old CMC registration code
- keep the local-only credential inventory in .env.credentials.local while leaving that file untracked

cdsmcp/docs/vm-lookup-and-assignment.md

@@ -47,8 +47,9 @@ This file covers vCenter VM lookup responses and the workflow for assigning exis
 - Never perform the assignment step until the operator explicitly approves after seeing that summary.
 
 ## Common VM Credentials
-- Username: `root`
-- Password: `cdsi2012`
+- Source `/home/aw/code/cds/.env.credentials.local`
+- Username: `ATVM_TARGET_USER`
+- Password: `ATVM_TARGET_PASSWORD`
 
 ## Status Output Format (Power-Off/Revert/Power-On)
 - `VM [vm name] was poweredOn, so I powered it off` (or `already poweredOff`)