fix: relax pydantic-core upper bound from <2.44.0 to <3

[vapi-tasker]

Summary

• Relaxes pydantic-core version constraint from >=2.18.2,<2.44.0 to >=2.18.2,<3 in both pyproject.toml and requirements.txt
• The <2.44.0 upper bound was auto-generated by the Fern SDK generator (fernapi/fern-python-sdk v5.3.3) in commit 7a070a7 and was not based on any actual API incompatibility
• Users with pydantic>=2.13.3 (which requires pydantic-core==2.46.3) were unable to install SDK v1.11.0, forcing them to downgrade to v1.9.0

Root Cause

The SDK only uses three stable pydantic-core APIs:

• PydanticUndefined (sentinel value comparison)
• core_schema (schema building in Rfc2822DateTime)
• to_jsonable_python (JSON serialization)

None of these APIs have changed across pydantic-core 2.x releases. The <2.44.0 cap was an artifact of the Fern code generator, not a deliberate compatibility boundary.

Changes

File	Change
pyproject.toml	pydantic-core = ">=2.18.2,<3"
requirements.txt	pydantic-core>=2.18.2,<3
poetry.lock	Regenerated (cosmetic metadata from Poetry 2.4.1)
tests/test_pydantic_core_compat.py	14 new tests verifying all pydantic-core usage patterns

Test plan

• All 14 new pydantic-core compatibility tests pass, covering every pydantic_core import in the SDK
• Full test suite passes (63 passed, 4 skipped for optional aiohttp)
• mypy type checking passes (2069 source files, no issues)
• ruff linting passes

Linear Issue

PRO-2816

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Note for maintainers: The Fern SDK generator may re-introduce this constraint on the next regeneration. Consider adding pyproject.toml and requirements.txt to .fernignore, or configuring the Fern generator to not pin pydantic-core with a restrictive upper bound.

🤖 Generated with Claude Code