ci: retain historical nightly assets

[tkkhq]

Summary

• keep a single visible nightly GitHub Release while appending versioned historical assets for each main build
• keep normal nightly assets clobbered for stable URLs and upload version-suffixed copies for retention
• keep creating the immutable semver nightly git tag for traceability
• allow the installer to fetch immutable nightly versions from the nightly release historical assets

Asset naming

• latest nightly: volcano-linux-amd64
• historical nightly: volcano-linux-amd64-v0.0.N-nightly.YYYYMMDD.NUMBER
• windows historical: volcano-windows-amd64-v0.0.N-nightly.YYYYMMDD.NUMBER.exe
• historical checksums: SHA256SUMS-v0.0.N-nightly.YYYYMMDD.NUMBER

Validation

• bash -n scripts/install-volcano.sh
• bash -n scripts/ci/resolve-cli-build-env.sh
• parsed .github/workflows/publish-cli.yml as YAML
• bash-checked publish step script
• locally smoke-tested historical asset name generation

[Copilot]

Pull request overview

This PR updates the nightly release pipeline to retain versioned “historical” nightly assets in the single nightly GitHub Release, while keeping the unversioned nightly assets clobbered for stable URLs. It also updates the installer to support fetching and signature-verifying immutable nightly versions from those retained assets.

Changes:

• Extend scripts/install-volcano.sh to accept v0.0.N-nightly.YYYYMMDD.NUMBER as a version selector (download URL + cosign verification identity handling).
• Update .github/workflows/publish-cli.yml to append version-suffixed copies of nightly assets and generate SHA256SUMS-<version> for the historical set.
• Improve installer error messages to include the new supported version selector format.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
scripts/install-volcano.sh	Adds versioned-nightly selector support for download URL construction and cosign verification.
.github/workflows/publish-cli.yml	Adds a step to duplicate nightly assets with a version suffix and emit version-specific checksum files while maintaining stable unversioned asset URLs.

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