fix: set workspace.baseDir to target directory on instances create/clone

[lngdao]

Summary

When creating or cloning an instance via openacp instances create --dir <path>, the workspace.baseDir in the generated config was hardcoded to ~/openacp-workspace. This caused agent sessions to operate in the wrong directory instead of the target folder.

Fix: Set workspace.baseDir to resolvedDir (the --dir path) for both clone and new instance flows.

Test plan

• openacp instances create --dir /tmp/test --no-interactive --json → config has workspace.baseDir: "/tmp/test"
• Clone from existing instance → new config has baseDir pointing to target directory
• Agent session in new workspace operates in correct directory