Fix intermittent exit code capture failure in SSH executeCommand

[synacktraa]

Problem

The executeCommand method was intermittently returning exit code 0 for commands that should fail (e.g., nonexistentcommand12345 should return 127). This happened because we were relying on the SSH2 exit event, which is optional according to the SSH2 specification.

Test Case That Was Failing

const failResult = await sandbox.runCommand('nonexistentcommand12345');
expect(failResult.exitCode).toBe(127); // Sometimes got 0 instead of 127

Root Cause

• SSH2 exit events are optional per the specification
• When the exit event doesn't fire, we were falling back to exit code 0
• This caused failed commands to appear successful intermittently

Solution

Stop relying on optional SSH2 events and capture exit codes at the command level:

1. Append exit code capture to every foreground command: ${command}; echo "EXIT_CODE:$?"
2. Parse from output by searching for the last line starting with EXIT_CODE:
3. Clean the output by removing the exit code line before returning
4. Maintain backward compatibility - no API changes

Testing

• Commands that fail now consistently return correct exit codes
• Commands that succeed still return exit code 0
• Output remains clean (exit code line removed)
• Background commands unaffected
• Ran the failing test 10 times - all passes

Impact

• Risk: Low - only changes internal implementation
• Benefit: High - eliminates flaky test failures and unreliable exit codes
• Compatibility: Full backward compatibility maintained

[synacktraa]

Made a new release with version 1.0.1 @jamesmurdza

[jamesmurdza]

All tests pass for me!