registry: add aqua for buck2 prereleases

[risu729]

Summary

• Add aqua:facebook/buck2 as the preferred backend for buck2.
• Preserve the existing GitHub fallback bin = "buck2" option.
• Set prerelease = true on both aqua and GitHub because all buck2 GitHub releases are marked prerelease.

Popularity

• GitHub: 4.3k stars, 347 forks, pushed 2026-05-12
• Releases: 70/70 recent GitHub releases are marked prerelease
• Existing mise registry entry: this changes backend selection for an already-registered tool

Testing

• mise ls-remote --no-versions-host github:facebook/buck2 returns no versions
• mise ls-remote --no-versions-host github:facebook/buck2[prerelease=true] | tail -5
• mise ls-remote --no-versions-host aqua:facebook/buck2[prerelease=true] | tail -5

[greptile-apps]

Greptile Summary

This PR updates registry/buck2.toml to add aqua:facebook/buck2 as the preferred backend for the buck2 tool, with the existing github:facebook/buck2 entry kept as a fallback.

• Aqua backend is inserted first (higher priority) with prerelease = true, since all buck2 GitHub releases are marked as prereleases.
• The GitHub fallback retains bin = "buck2" and gains the same prerelease = true flag so version listing works without a manual override.

Confidence Score: 5/5

Single-file registry TOML change with no logic modifications — safe to merge.

The change is a purely declarative registry update. The TOML structure matches the pattern used by other multi-backend entries in the registry, prerelease = true is a documented and tested option for both the aqua and github backends, and the existing bin = "buck2" option on the GitHub fallback is preserved.

No files require special attention.

Important Files Changed

Filename	Overview
registry/buck2.toml	Adds aqua:facebook/buck2 as the preferred backend with prerelease = true, and adds the same flag to the existing GitHub fallback while preserving bin = "buck2".

_{Reviews (2): Last reviewed commit: "Merge branch 'main' into registry/buck2-..." | Re-trigger Greptile}

[gemini-code-assist]

Code Review

This pull request updates the registry/buck2.toml file by adding a new aqua:facebook/buck2 backend and enabling the prerelease option for both the new backend and the existing github:facebook/buck2 backend. I have no feedback to provide.