chore!: drop python 3.9 add 3.14

[JP-Ellis]

📝 Summary

Add support for Python 3.14, and drop support for Python 3.9 as it has reached its end-of-life.

🚨 Breaking Changes

Python 3.9 is no longer supported.

🔥 Motivation

🔨 Test Plan

🔗 Related issues/PRs

[Copilot]

Pull Request Overview

This PR modernizes the Python support by adding support for Python 3.14 and dropping support for Python 3.9 (which has reached end-of-life). The changes include updating type annotations to use modern Python syntax and removing dependencies on typing-extensions for Python 3.10+.

• Adds Python 3.14 support and removes Python 3.9 support across all project configurations
• Updates type annotations to use modern Python union syntax (str | None instead of Union[str, None])
• Moves imports that require newer Python versions into TYPE_CHECKING blocks for better compatibility

Reviewed Changes

Copilot reviewed 41 out of 41 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
pyproject.toml	Updates Python version support from 3.9-3.13 to 3.10-3.14, removes typing-extensions dependency for runtime
src/pact/types.py	Modernizes type annotations using union operator syntax
src/pact/verifier.py	Consolidates imports and removes Python 3.9 compatibility code
Multiple test files	Adds from __future__ import annotations imports for forward compatibility
GitHub workflows	Updates CI configuration to test Python 3.10-3.14 instead of 3.9-3.13
Example projects	Updates minimum Python requirement and modernizes type annotations

---

_{Tip: Customize your code reviews with copilot-instructions.md. Create the file or learn how to get started.}

[codecov]

Codecov Report

❌ Patch coverage is 91.66667% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 52%. Comparing base (0e3942f) to head (05baf4d).
⚠️ Report is 2 commits behind head on main.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
src/pact/verifier.py	75%	1 Missing ⚠️

Additional details and impacted files

@@         Coverage Diff          @@
##           main   #1263   +/-   ##
====================================
- Coverage    52%     52%   -1%     
====================================
  Files        32      32           
  Lines      3740    3739    -1     
====================================
- Hits       1967    1966    -1     
  Misses     1773    1773           

Flag	Coverage Δ
tests	52% <91%> (-1%)	⬇️

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

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.