fix(service): preserve slotted service subclasses with compiled core runtime

[cofin]

Summary

Keep SQLSpecAsyncService and SQLSpecSyncService as ordinary slotted Python classes in sqlspec.service._base while retaining compiled query execution and transaction helpers in the private sqlspec.service._core runtime. Downstream consumers and frameworks (such as Litestar and Advanced Alchemy) preserve generic typing and __slots__ without native class layout restrictions or slotscheck exclusions.

Changes

• Service Architecture (sqlspec/service/):
  • Organized sqlspec/service into a package with explicit re-exports in __init__.py.
  • Moved service bases to sqlspec/service/_base.py as pure slotted Python classes (excluded from mypyc compilation).
  • Moved core query execution and transaction management into sqlspec/service/_core.py (compiled via hatch-mypyc).
• Driver & Base Classes:
  • Maintained native extension classes for driver connection contexts, session factories, and exception handlers across sqlspec/driver/.
• Tooling & CI:
  • Added compiled-wheel smoke test suite (tools/scripts/mypyc_smoke.py and tools/scripts/mypyc_inventory.py) testing multi-level slotted subclasses, transaction contexts, and session acquisition.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 95.03546% with 14 lines in your changes missing coverage. Please review.
✅ Project coverage is 78.93%. Comparing base (47ed4b7) to head (b49b288).

Files with missing lines	Patch %	Lines
sqlspec/service/_core.py	94.81%	9 Missing and 5 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #785      +/-   ##
==========================================
- Coverage   78.93%   78.93%   -0.01%     
==========================================
  Files         491      493       +2     
  Lines       72316    72337      +21     
  Branches    10165    10165              
==========================================
+ Hits        57081    57096      +15     
- Misses      11730    11736       +6     
  Partials     3505     3505              

Flag	Coverage Δ
integration	62.44% <75.17%> (+<0.01%)	⬆️
py3.10	77.06% <95.03%> (+<0.01%)	⬆️
py3.11	77.06% <95.03%> (-0.01%)	⬇️
py3.12	77.07% <95.03%> (+<0.01%)	⬆️
py3.13	77.06% <95.03%> (+<0.01%)	⬆️
py3.14	78.20% <95.03%> (+<0.01%)	⬆️
unit	67.28% <95.03%> (+<0.01%)	⬆️

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

Files with missing lines	Coverage Δ
sqlspec/service/__init__.py	100.00% <100.00%> (ø)
sqlspec/service/_base.py	96.82% <100.00%> (ø)
sqlspec/service/_core.py	94.81% <94.81%> (ø)

... and 2 files with indirect coverage changes

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