Release 3.0.0-preview.8

[mtmk]

Preview release on the 3.0 line bumping version to 3.0.0-preview.8.

• Add OTel metrics support (Add OTel metrics support #1154)

[synadia-claude-reviewer]

Claude finished @mtmk's task in 40s —— View job

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PR Review: Release 3.0.0-preview.8

• Gather context (diff, CLAUDE.md, changed files)
• Review changes
• Post findings

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This is a single-line version bump (version.txt: 3.0.0-preview.7 → 3.0.0-preview.8). No issues found.

• src/Directory.Build.props reads version.txt directly via MSBuild to set the NuGet <Version> and <PackageVersion> — the bump will propagate to all packages automatically.
• release.yml validates that the git tag matches version.txt at release time — the change is consistent with that expectation.

No correctness, security, or performance concerns. The change is correct and ready to merge.

[scottf]

LGTM