Improve testing of interactive commands

[klieret]

• Typing fixes and docstrings
• Extract interactive command handling into InteractiveSession

[codecov]

Codecov Report

Attention: Patch coverage is 71.52778% with 41 lines in your changes missing coverage. Please review.

Project coverage is 75.25%. Comparing base (0aef099) to head (ebdc379).
Report is 18 commits behind head on main.

Files with missing lines	Patch %	Lines
sweagent/agent/interactive_commands.py	64.76%	37 Missing ⚠️
sweagent/environment/swe_env.py	84.61%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #804      +/-   ##
==========================================
+ Coverage   73.33%   75.25%   +1.91%     
==========================================
  Files          31       31              
  Lines        4568     4599      +31     
==========================================
+ Hits         3350     3461     +111     
+ Misses       1218     1138      -80     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.