Fix Python float/int validation against float64/int64 specs

[rly]

Summary

• Python native float is 64-bit, but get_type() was returning "float" which aliases to float32 in the spec system, causing validation failures against float64 specs
• Same issue for Python native int (64-bit or larger) returning "int" which aliases to int32
• Fixed get_type() to return "float64" for Python float and "int64" for Python int
• Uses exact type check (type(data) is float) to avoid catching numpy subclasses or bool
• Backward compatible: specs expecting float32/int32 already accept float64/int64 via additional_allowed

Fixes #1368

Test plan

• Added test: Python float validates against float64 spec (was failing, now passes)
• Added test: Python int validates against int64 spec (was failing, now passes)
• Added test: Python float still validates against float (float32) spec (regression check)
• Added test: Python int still validates against int (int32) spec (regression check)
• All 91 validator tests pass

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.85%. Comparing base (b1f381a) to head (7d2bd71).
⚠️ Report is 1 commits behind head on dev.

Additional details and impacted files

@@           Coverage Diff           @@
##              dev    #1410   +/-   ##
=======================================
  Coverage   92.84%   92.85%           
=======================================
  Files          41       41           
  Lines        9986     9990    +4     
  Branches     2052     2054    +2     
=======================================
+ Hits         9272     9276    +4     
  Misses        436      436           
  Partials      278      278           

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