#1747: use macos-15-intel runner for x64 native image build

[shodiBoy1]

This PR fixes #1747

Implemented changes:

• Changed GitHub Actions macOS x64 runner from macos-15 to macos-15-intel in release and nightly-build workflows
• Updated assembly descriptor release-mac-x64.xml to reference the correct artifact name natives-macos-15-intel
• Added changelog entry

Root cause: Both macos-latest and macos-15 resolve to ARM (Apple Silicon) runners (reference), so the mac-x64 package was shipping an arm64 binary instead of an x64 one.

Verified: Downloaded ide-cli-2026.03.001-mac-x64.tar.gz on Intel MacBook Pro (2015, Monterey 12.7.6), ran file bin/ideasy -> confirmed it contains an arm64 binary instead of x64.

Note: Cannot be fully tested locally since native images are built by GitHub Actions. Fix is based on GitHub's documented runner architectures.

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[coveralls]

Pull Request Test Coverage Report for Build 23274666150

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.005%) to 70.631%

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Totals
Change from base Build 23195347152:	0.005%
Covered Lines:	10769
Relevant Lines:	14648

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💛 - Coveralls

[hohwille]

@shodiBoy1 thanks for your PR. Awesome that you found the reason. 👍
We had macos-13 before that was on x64 and upgraded to macos-15 so we did not expect that this changed from x64 to arm64. Since arm64 is meanwhile the standard for MacOS it surely makes sense.
Ready for merge.