Prevent STELLAR_SIGN_WITH_KEY from showing up on stellar env.

[fnando]

What

Prevent STELLAR_SIGN_WITH_KEY from showing up on stellar env.

Before:

$ STELLAR_SIGN_WITH_KEY=foo STELLAR_SECRET_KEY=bar stellar env
STELLAR_ACCOUNT=default   # use
STELLAR_NETWORK=local     # use
STELLAR_SIGN_WITH_KEY=foo # env

After:

$ STELLAR_SIGN_WITH_KEY=foo STELLAR_SECRET_KEY=bar stellar env
STELLAR_ACCOUNT=default # use
STELLAR_NETWORK=local   # use

Why

STELLAR_SIGN_WITH_KEY can also contain a secret key.

Known limitations

N/A

[Copilot]

Pull request overview

This PR addresses a security concern by preventing STELLAR_SIGN_WITH_KEY from being displayed when running the stellar env command, since this environment variable can contain secret keys. The fix follows the same pattern already established for STELLAR_SECRET_KEY.

Changes:

• Removed SIGN_WITH_KEY from the public environment variables list to prevent it from being displayed by stellar env
• Manually added SIGN_WITH_KEY to the backwards compatibility mapping (SOROBAN_* to STELLAR_*) to maintain functionality
• Added comprehensive test coverage for both STELLAR_SECRET_KEY and STELLAR_SIGN_WITH_KEY to verify they are properly excluded from the env command output

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
cmd/soroban-cli/src/env_vars.rs	Removed SIGN_WITH_KEY from the unprefixed environment variables list that gets displayed
cmd/soroban-cli/src/cli.rs	Added SIGN_WITH_KEY to the manual list for backwards compatibility mapping while preventing display
cmd/crates/soroban-test/tests/it/config.rs	Added PredicateBooleanExt import and two test cases to verify SECRET_KEY and SIGN_WITH_KEY are not displayed in env output