fix(cli): use renamed macOS standalone assets

[JP-Ellis]

📝 Summary

pact-standalone publishes its macOS archives as pact-{version}-macos-{arch}.tar.gz from 2.6.1 onwards. Releases up to 2.6.0 used osx. The build hook still requests the osx name, so release PR #1609 (pact-python-cli 2.6.4.0) gets a 404 on both macOS runners. Upstream's release notes still show the old osx URLs.

This PR picks the name from the version: macos from 2.6.1, osx before it. main still declares 2.6.0.1, so the check keeps main building until #1609 bumps the version. The Linux and Windows asset names did not change. The 2.6.4 archive has the same pact/bin and pact/lib layout and the same seven Ruby tools as 2.6.0.

🔥 Motivation

2.6.4.0 is planned as the last pact-python-cli release built from this repository. Later releases will come from pact-foundation/pact-cli and bundle only the Rust pact binary. #1723 deletes this build hook.

🔨 Test Plan

• Built the CLI wheel on macOS arm64 at 2.6.0.1 (downloaded pact-2.6.0-osx-arm64.tar.gz), and with the version temporarily set to 2.6.4.0 (downloaded pact-2.6.4-macos-arm64.tar.gz).
• Installed that wheel in a clean venv and ran the bundled pact-broker version, which printed 1.78.0.
• CI on chore(release): pact-python-cli v2.6.4.0 #1609 is the end-to-end check across all six build runners.

🔗 Related issues/PRs

Stack: #1721 → #1722 → #1723.

Release order:

1. Merge this PR. The release job refreshes chore(release): pact-python-cli v2.6.4.0 #1609 at 2.6.4.0.
2. Merge chore(release): pact-python-cli v2.6.4.0 #1609 once its macOS builds pass. That publishes pact-python-cli 2.6.4.0.
3. Merge feat!: remove pact.v2 compatibility module #1722 and chore(cli): remove pact-python-cli #1723.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 74%. Comparing base (0aa5952) to head (4fd1e8c).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@         Coverage Diff          @@
##           main   #1721   +/-   ##
====================================
  Coverage    74%     74%           
====================================
  Files        36      36           
  Lines      4109    4109           
====================================
  Hits       3063    3063           
  Misses     1046    1046           

Flag	Coverage Δ
examples	36% <ø> (ø)
tests	73% <ø> (ø)

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