ci: pin package build SDK

[dansiegel]

Cleanup note: I removed stale bot inline/duplicate comments and rewrote Dan-authored review notes here to read naturally. The remaining ### 💡 Codex Review entries are submitted bot review records and can’t be edited/deleted via API, so I left them in place for traceability.

[dansiegel]

Reviewed the workflow/toolchain diff in ci.yml, pr.yml, start-release.yml, and global.json.

I didn’t see any permission or deploy-path changes from this update. The release job still only writes to its existing target, and code-sign/feed secrets stay as GitHub secrets. actionlint and PR checks are green.

I can’t submit a formal approval on my own PR, so this is posted as a review note.

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: fecfd9492c

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: 0cf254c00d

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".

[dansiegel]

Update: the earlier security note is stale. This iteration now uses the .NET 8 train (8.0.x) in both MSBuild and PR/e2e paths, and it no longer pins an exact SDK patch version. global.json remains non-exact with preview disabled for release builds.

[dansiegel]

I cleaned up a few stale review notes. The remaining Codex review entries are GitHub’s submitted review records, so I’m leaving them for traceability.