fix(#668): harden storage payload codecs

[cofin]

Summary

• decode JSONL payloads through PyArrow's native JSON reader
• reject unsupported row/Arrow storage write-format combinations before side effects
• document native inference and the full-payload memory boundary

Details

Exact empty JSONL payloads preserve the existing empty-table result; ordinary JSON arrays retain their existing decoder. Invalid sync and async writes now fail before serialization, encoding, backend resolution, I/O, or diagnostic telemetry.

Closes #668.
Closes #669.

Verification

• 17 focused payload tests and full storage unit suite
• Ruff and focused mypy
• mypyc performance build
• 100k-row JSONL benchmark improved from 0.189508s to 0.027407s mean

[codecov-commenter]

Codecov Report

❌ Patch coverage is 96.29630% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 77.28%. Comparing base (a3a3012) to head (be17fdb).

Files with missing lines	Patch %	Lines
sqlspec/storage/pipeline.py	93.75%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #672      +/-   ##
==========================================
+ Coverage   77.26%   77.28%   +0.02%     
==========================================
  Files         475      475              
  Lines       67901    67920      +19     
  Branches     9335     9338       +3     
==========================================
+ Hits        52462    52494      +32     
+ Misses      12035    12025      -10     
+ Partials     3404     3401       -3     

Flag	Coverage Δ
integration	60.79% <33.33%> (-0.02%)	⬇️
py3.10	75.60% <96.29%> (+0.02%)	⬆️
py3.11	64.52% <96.29%> (-11.07%)	⬇️
py3.12	75.61% <96.29%> (+0.03%)	⬆️
py3.13	75.62% <96.29%> (+1.38%)	⬆️
py3.14	76.49% <96.29%> (+0.03%)	⬆️
unit	64.81% <96.29%> (+0.03%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
sqlspec/storage/_arrow_payload.py	93.33% <100.00%> (+34.24%)	⬆️
sqlspec/storage/_utils.py	97.43% <100.00%> (+0.29%)	⬆️
sqlspec/storage/pipeline.py	86.19% <93.75%> (+1.03%)	⬆️

... and 2 files with indirect coverage changes

🚀 New features to boost your workflow:

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