`stacker target server` doesn't use EXISTING_SERVER_KEY from .env

[vsilent]

Description

When switching target to an existing server, the CLI stores ssh_key: null in the deployment lock instead of reading EXISTING_SERVER_KEY from the environment.

Affected Projects

Mastodon

Steps to Reproduce

1. Define EXISTING_SERVER_KEY=./stacker-project-test in .env
2. Source .env
3. Run stacker target server with piped input
4. Inspect .stacker/deployment-server.lock

Expected Behavior

ssh_key in the lock file should be set to the provided key path.

Actual Behavior

ssh_key: null is written to the lock file. Subsequent deploys fail with:

Authentication failed: Public key authentication failed

Current Workaround

Manually edit .stacker/deployment-server.lock to set ssh_key to the correct path.

Environment

• Stacker CLI version: latest
• Deploy target: server