chore(forge): avoid process::exit in results

[radik878]

Motivation

The TestOutcome::ensure_ok method calls std::process::exit(1), which makes the library code difficult to reuse (impossible to intercept/handle on the caller's side).

Solution

Replaced both calls to std::process::exit(1) in ensure_ok with a return to Err(...). This matches the method signature and the general error model in the project.
To avoid “breaking” quiet modes (JUnit/JSON) with an additional error string, I corrected the high-level error printing in crates/forge/bin/main.rs. Now sh_err!(“{err:?}”) is definitely printed there before process::exit(1). It is enough to wrap the print with a condition: do not print if shell::is_quiet() or shell::is_json(), but only set the exit code to 1.

PR Checklist

• Added Tests
• Added Documentation
• Breaking changes