feat: add metadata JSON readiness output

[panva]

This adds structured readiness output to git node metadata --json so automation can consume PR landability checks without matching human-readable CLI output.

The JSON output includes:

• ready
• readiness
• exitCode
• metadata
• reasonCodes
• reasons

It also adds stable reason codes from PRChecker for the existing readiness checks.

Exit Codes

git node metadata --json uses category-level exit codes:

• 0: PR is ready
• 20: PR is not ready for deferrable metadata reasons
• 40: PR is not ready for a hard or mixed reason
• 1: unexpected tool/runtime failure

20-29 are reserved for future deferrable metadata states, and 40-49 are reserved for future hard metadata failure states.

The current deferrable set is scoped to the lightweight commit-queue selector use case from nodejs/node#64343:

• missing-approval
• missing-tsc-approval
• wait-time

[codecov]

Codecov Report

❌ Patch coverage is 87.45387% with 34 lines in your changes missing coverage. Please review.
✅ Project coverage is 62.43%. Comparing base (9250fba) to head (733f3a8).

Files with missing lines	Patch %	Lines
lib/pr_checker.js	92.63%	12 Missing ⚠️
components/git/metadata.js	67.64%	11 Missing ⚠️
components/metadata.js	85.13%	11 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1113      +/-   ##
==========================================
+ Coverage   62.01%   62.43%   +0.42%     
==========================================
  Files          46       48       +2     
  Lines        7505     7882     +377     
==========================================
+ Hits         4654     4921     +267     
- Misses       2851     2961     +110     

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[aduh95]

The current deferrable set is scoped to […]:

• missing-approval
• missing-tsc-approval
• wait-time

Can we change that to only capture wait time? E.g. missing TSC approval should be a hard error, no amount of time is going to help with that, and not erroring would be confusing IMO. Missing approval would mean that someone has added the CQ label on a 0-approval PR, again that seems like an error

[panva]

@aduh95 makes sense, i'll update the utils and then the node PR

[aduh95]

LGTM, we might also want to add PENDING_CI as deferable, so we can clean up https://github.com/nodejs/node/blob/db7cc5b40018e685f9f409b382884f84dec71c65/tools/actions/commit-queue.sh#L42-L46

[panva]

I'm not sold on pending ci. With how flaky ci can get i think noone should be adding cq to a PR with an in progress ci. As such the cleanup you speak of would be imho better suited to go in the other direction.

[aduh95]

That's fine by me. I think the idea is to get the CQ to notify you if the CI failed