[Companion]

Fixes #259

Fix

Return an error when the registry rejects a publish so the CLI exits unsuccessfully and writes the status and response body to stderr

Successful publishes keep their existing message and exit status

Tests

• Added real CLI regressions using isolated local registries for 401 422 and 500 responses
• All three error regressions fail before the fix and pass after it
• Verified 200 201 and 204 responses still succeed
• Full all features workspace suite passed with 65 tests passed and one existing test ignored
• Formatting build and Clippy with all features and all targets passed
• Clippy reports existing warnings outside the changed files