Use pre-fixed jigsaw_v2 HTML and expand test coverage

[blink1073]

References

Follow up to #375

Description

Moves the cross-origin postMessage fixes out of jigsaw_magic.py and into the upstream HTML source files (now served from calysto.github.io/jigsaw_v2/). The magic no longer needs to patch downloaded HTML at runtime — it only fills in the window.__jigsaw_saved_xml__ placeholder that is already baked into the v2 files.

Changes

• Remove _fix_cross_origin() function from jigsaw_magic.py (~127 lines)
• Update download URL from jigsaw/ to jigsaw_v2/
• Replace _fix_cross_origin() call with a single targeted string replacement for the saved-XML placeholder
• Delete scripts/reproduce_196.py (referenced the now-removed function)
• Parametrize jigsaw tests across all three languages: Processing, Python, Test
• Add test_jigsaw_html_content to assert postMessage helpers are present and no window.parent property assignments remain
• Switch all test file output to pytest tmp_path (no files written to the repo directory)
• Remove manual teardown() function

Backwards-incompatible changes

None

Testing

just test tests/magics/test_jigsaw_magic.py — 10/10 tests pass across all three languages.

AI usage

• Some or all of the content of this PR was generated by AI.
• The human author has carefully reviewed this PR and run this code.
• AI tools and models used: Claude Sonnet 4.6 (Claude Code)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.79%. Comparing base (47b7214) to head (b57d490).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #385      +/-   ##
==========================================
- Coverage   90.86%   90.79%   -0.08%     
==========================================
  Files          51       51              
  Lines        2957     2943      -14     
  Branches      414      414              
==========================================
- Hits         2687     2672      -15     
  Misses        190      190              
- Partials       80       81       +1     

Files with missing lines	Coverage Δ
metakernel/magics/jigsaw_magic.py	79.59% <100.00%> (-6.13%)	⬇️

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.