Stream filesystem conversions into output

[timkpaine]

Description

Add Python file-like codec writers and stream DataFileSystem conversions directly into the seekable output spool. Apply schema plans batch by batch without collecting decoded batches or intermediate encoded bytes.

Type of Change

• Bug fix
• New feature
• Documentation update
• Refactor / code cleanup
• CI / build configuration
• Other (describe below)

Checklist

• Linting passes (make lint)
• Tests pass (make test)
• New tests added for new functionality
• Documentation updated (if applicable)
• Changelog / version bump (not applicable)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.93%. Comparing base (76820be) to head (54f0ebb).

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #54      +/-   ##
==========================================
+ Coverage   94.48%   94.93%   +0.45%     
==========================================
  Files          11       11              
  Lines         580      632      +52     
  Branches       26       30       +4     
==========================================
+ Hits          548      600      +52     
  Misses         29       29              
  Partials        3        3              

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[github-actions]

Test Results

60 tests  +7   60 ✅ +7   0s ⏱️ ±0s
 1 suites ±0    0 💤 ±0 
 1 files   ±0    0 ❌ ±0 

Results for commit 54f0ebb. ± Comparison against base commit 76820be.

♻️ This comment has been updated with latest results.