remove fits extension assumption for hooks

[braingram]

This PR updates hooks to inherit output_ext from the hooked class.

Closes #216

JWST regtests: https://github.com/spacetelescope/RegressionTests/actions/runs/12938827091
Roman regtests: https://github.com/spacetelescope/RegressionTests/actions/runs/12968661316

Regtests all passed

Tasks

• update or add relevant tests
• update relevant docstrings and / or docs/ page
• Does this PR change any API used downstream? (if not, label with no-changelog-entry-needed)
  • write news fragment(s) in changes/: echo "changed something" > changes/<PR#>.<changetype>.rst (see below for change types)
  • run regression tests with this branch installed ("git+https://github.com/<fork>/stpipe@<branch>")
    • jwst regression test
    • romancal regression test

news fragment change types...

• changes/<PR#>.feature.rst: new feature
• changes/<PR#>.bugfix.rst: fixes an issue
• changes/<PR#>.doc.rst: documentation change
• changes/<PR#>.removal.rst: deprecation or removal of public API
• changes/<PR#>.misc.rst: infrastructure or miscellaneous change

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.37%. Comparing base (c947ebd) to head (d776d14).
Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #217      +/-   ##
==========================================
+ Coverage   95.28%   95.37%   +0.09%     
==========================================
  Files          37       37              
  Lines        3178     3245      +67     
==========================================
+ Hits         3028     3095      +67     
  Misses        150      150              

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

[nden]

The Roman example now works.