Respect required CI checks

[lukelabonte]

Summary

This updates MonitorLizard so the main PR status is based on the checks GitHub actually treats as required.

Before this, optional checks could make a PR look blocked even when GitHub would allow it to merge. That was noisy for repos that use approval-gated CircleCI workflows. Now required checks drive the main status, and approval-gated non-blocking checks show up on a separate line.

What changed

• Fetch required check metadata from GitHub's GraphQL API.
• Treat missing required contexts as pending, so a required check that hasn't reported yet doesn't look green.
• Keep non-required checks out of the main merge-blocking status.
• Show approval-gated non-blocking checks as a small secondary row, like Non-blocking: 1 waiting for approval.
• Keep non-blocking failures out of the failing-check expansion, but still show other failed checks.
• Added tests for required-check handling, missing required contexts, and the non-blocking summary.

Screenshots

Verification

• xcodebuild -project "MonitorLizard/MonitorLizard.xcodeproj" -scheme "MonitorLizard" -configuration Debug CODE_SIGNING_ALLOWED=NO build
• git diff --check

I also tried a focused test run for the GitHub service tests. The test bundle still fails to compile because of existing Swift 6 actor-isolation errors in PRMonitorViewModelTests.swift, so those tests don't get far enough to run yet.

[SeanMcTex]

Thanks a bunch for the submission! Would definitely like to avoid CircleCI-specific code if at all possible, since not everyone uses it. I'd be glad for your thoughts.

[lukelabonte]

I pushed another pass based on the review.

What changed:

• Removed the CircleCI-specific matching.
• Switched required CI detection to GitHub's own metadata (isRequired, with branch protection contexts as a fallback).
• Kept the main PR status focused on merge-blocking CI.
• Moved optional checks into the separate Non-blocking: summary.
• Added Not started for required CI that hasn't kicked off yet.
• Added fallback handling for rollup-only GitHub states, including EXPECTED as pending.
• Reused the same GraphQL status parsing path for batch fetches, single PR status fetches, and Other PRs.
• Fixed a couple of follow-up edge cases around .notStarted and waiting approval parent checks.