fix(instrumentation): remove process.once Edge warnings

[puxiao]

Summary

This removes two build-time Edge warnings that occur during pnpm dev, while preserving the existing Node-side shutdown behavior.

Related Issues

Fixes #1262

Changes

• Add lib/server/shutdown-signals.ts with registerShutdownSignals(shutdown).
• In instrumentation.ts, replace the inline process.once calls with a dynamic import and call:
  await import('@/lib/server/shutdown-signals') → registerShutdownSignals(shutdown).

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update
• Refactoring (no functional changes)
• CI/CD or build changes

Verification

Steps to reproduce / test

1. Run pnpm dev — before the fix, this triggered two warnings at instrumentation.ts
2. After the fix, pnpm dev runs without the warnings, and pnpm build remains unaffected.

[LING-6150]

Thanks for the focused patch. The implementation itself looks appropriately scoped, and I don’t have any code-level blockers.
Before merging, please correct the PR title/body and #1262 so they match the observed behavior.
With Next.js 16.1.2, the inline process.once calls produce two Edge Runtime warnings, but next build still completes successfully with exit code 0. This patch removes those warnings; it does not fix a compile failure.
I also reproduced the warnings with a Node-runtime proxy.ts and an empty Edge middleware manifest, so having an explicit Edge runtime entry is not a required condition.
Please update:

• The PR title and summary to describe removing Edge build warnings rather than fixing a compile failure.
• The verification section to state that the build succeeds before and after the patch.
• #1262’s title/body and reproduction conditions accordingly.
• The malformed Closes #1262" reference.
  An accurate framing would be: this removes two build-time Edge warnings while preserving the existing Node-side shutdown behavior. In addition, please also modify the title as "fix(instrumentation): remove process.once Edge warnings" .
  No code changes are requested.

[LING-6150]

Thanks for addressing the review feedback so promptly. I’ve confirmed that this patch removes the two non-blocking Edge warnings while preserving the existing Node-side behavior.
After considering the maintenance tradeoff, we don’t plan to take a warning-only cleanup with no functional or user-facing impact at this time. The build already succeeds without this change, so I’m going to close the PR.
We can revisit this if the warning becomes blocking or needs to be addressed as part of a broader Next.js upgrade. Thanks again for the contribution.