Reject non-finite values in embedding vectors

[henryperkins]

Summary

• Reject NAN, INF, and -INF at the Embedding constructor boundary.
• Preserve the existing behavior for finite floats and integers.
• Add regression coverage for each non-finite value.

Fixes #262.

Why

Non-finite values satisfy PHP's is_float() check but cannot be represented in JSON. Rejecting them when constructing an Embedding prevents an invalid result object from failing later during serialization, logging, caching, persistence, or custom provider handling.

Testing

A test-only commit first demonstrated the gap: all three new cases failed because no InvalidArgumentException was thrown.

After the implementation commit:

• Unit tests pass on PHP 7.4, 8.0, 8.4, and 8.5.
• The PHP 8.4 coverage job passes.
• Composer validation, PHPStan, and PHPCS pass.

AI assistance

• AI assistance: Yes
• Tool: OpenAI Codex
• Used for: Repository inspection, regression-test design, implementation, and verification. Henry reviewed the scope and remains responsible for the contribution.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.50%. Comparing base (a31b0ec) to head (1cd9a52).

Additional details and impacted files

@@            Coverage Diff            @@
##              trunk     #263   +/-   ##
=========================================
  Coverage     86.49%   86.50%           
- Complexity     1327     1330    +3     
=========================================
  Files            68       68           
  Lines          4295     4298    +3     
=========================================
+ Hits           3715     3718    +3     
  Misses          580      580           

Flag	Coverage Δ
unit	86.50% <100.00%> (+<0.01%)	⬆️

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[github-actions]

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[henryperkins]

One downstream coordination note: WordPress/wordpress-develop#12530 currently imports PHP AI Client 1.4.0 for the WordPress 7.1 embedding API, so its vendored Embedding.php contains this same validation gap.

If this fix looks right, would a 1.4.1 patch release followed by updating #12530 to that tag be the cleanest path? I’m not suggesting this should block the Core wrapper review—just flagging the dependency while the import is still open.