Bump macos versions for artifacts

[ctz]

macos-13 runners are deprecated as of 8th December: https://github.blog/changelog/2025-09-19-github-actions-macos-13-runner-image-is-closing-down/

The Intel runner is moved to macos-15-intel, which is the final Intel macos platform that actions supports. The arm64 runner is updated to match.

[cpu]

Odd, it looks like the Windows CI jobs are failing to download + unzip pre-built cargo-c, but proceed to the next steps of the build anyway and then bail on the first usage of a cargo-c subcommand w/ cargo 🤔

[cpu]

it looks like the Windows CI jobs are failing to download + unzip pre-built cargo-c

Just classic GitHub stuff ™️ and it went away after a kick.

but proceed to the next steps of the build anyway and then bail on the first usage of a cargo-c subcommand w/ cargo

Trying to fix that separately: #624

[ctz]

I put this to draft because I assumed I had done something stupid and couldn't figure it out, lol.