fix(ng-dev/pr): harden CLA status check, automation target validation, TGP comment freshness, and log symlink guard

[josephperrott]

Summary

Hardens PR merge validation and local CLI logging against edge-case status, label, comment timestamp, and symlink checks:

1. CLA commit status verification (assertSignedCla & getStatusesForPullRequest):
   • Require type === "status" in assertSignedCla when verifying cla/google.
   • Prefix statusMap keys in getStatusesForPullRequest with check: and status: and add the missing break; statement under case "CheckRun": so a CheckRun cannot overwrite a StatusContext with the same name.
2. Automation target label bot-author check (assertChangesAllowForTargetLabel):
   • Enforce the automationBots author allowlist for target: automation before the merge: fix commit message early return.
3. TGP comment freshness check (assertEnforceTested):
   • Include commit committedDate/pushedDate and comment createdAt in GraphQL schemas and verify in pullRequestHasValidTestedComment that TESTED= comments from Googlers were created at or after the latest commit timestamp when timestamps are available.
4. Dangling symlink detection in .ng-dev.log guard (captureLogOutputForCommand):
   • Use lstatSync(logFilePath, {throwIfNoEntry: false})?.isSymbolicLink() so dangling symlinks are also rejected before opening .ng-dev.log.

[gemini-code-assist]

Code Review

This pull request enhances pull request validation by ensuring that TESTED comments are fresh (created after the latest commit), preventing CheckRuns from overwriting failing CLA StatusContexts, and ensuring automation target label checks are not bypassed by commit message fixup labels. It also refactors the logging utility to securely handle symbolic links. The review feedback suggests keeping the comment creation date as a required property to avoid correctness bypasses, and explicitly handling cases where the comment creation date is missing during freshness checks to prevent stale comments from being incorrectly treated as fresh.