chore: track upstream safe-settings bugs blocking workflow simplification

[marcusburghardt]

Summary

The Safe Settings Sync workflow includes three workarounds for upstream
bugs in safe-settings v2.1.18. This issue tracks when we can remove
them.

Upstream bugs

Bug	Issue	Fix	Status	Workaround
Probot v14 null logger	#955	None	Open	Pin to v2.1.18 (Probot v13)
check_suite crash in full-sync	#818	PR #1018	Open (not merged)	Patched full-sync.js
Repo name mutation	#901	PR #943	Merged to main-enterprise, not released	Sequential per-repo sync

Interdependencies

• Cannot upgrade past v2.1.18 until #955 is resolved (Probot v14).
• PR #943 fixes #901 but only in versions using Probot v14 (v2.1.21+),
  which we cannot use until #955 is also fixed.
• All three must be resolved in a single upstream release before we can
  drop the workarounds.

What to do when fixed

1. Update SAFE_SETTINGS_DEFAULT_VERSION to the new release SHA.
2. Remove full-sync-patched.js and revert to npm run full-sync.
3. Remove the sequential per-repo loop and revert to a single sync call.
4. Search for TODO(safe-settings-818) and TODO(safe-settings-name-mutation)
   to find all workaround code.
5. Update MAINTAINING.md "Known upstream workarounds" section.

Periodic check

Review the upstream issues quarterly or when a new safe-settings
release is tagged.