Feature request: opt out of auto-update / pin a version for Macs below the new minimum OS

This is a feature request about the update mechanism, not a bug report about macOS 12 support. I accept the decision in #37019 / #37070 to raise the minimum macOS to 13. The problem is the downstream consequence for users on hardware that cannot upgrade past Monterey, and the lack of any opt-out.

Context

• MacBook Pro A1707 (2017, Intel). macOS 12.7.6 Monterey is the hardware ceiling — this machine will never run macOS 13.
• Codex desktop worked fine on build 6119 (26.727.x).
• Sparkle auto-updated to build 6223+ → app no longer launches (NSOSStatusErrorDomain Code=-10825, LC_BUILD_VERSION minos 13.0).
• The workaround from @gpeal (download 26.715.72359) works — but only until Sparkle runs again and re-installs the broken build.

The gap

Once a Mac is on an OS below the new minimum, there is no supported way to stay on the last-working version:

1. Sparkle's appcast still advertises minimumSystemVersion 12.0, so the incompatible update keeps being offered.
2. There is no "disable auto-update" toggle in the app.
3. There is no "check for updates but let me choose" option.
4. There is no documented way to pin a version.

The only way to stay on 26.715 is to block oaistatic.com at the network level — not something most users will figure out, and it also blocks legitimate downloads.

Request

Any one of these would unblock users on unsupported-but-still-functional hardware:

1. Fix the Sparkle appcast minimumSystemVersion to 13.0 so macOS 12 clients stop being offered the incompatible build. (This is also just correct — the manifest should match the binary.)
2. Add a "Check for updates but let me choose to install" option, or a "Disable auto-update" toggle in Settings.
3. Document a supported way to pin a version (a defaults key, a config file, or a "skip this version" action in the update prompt).

I'm not asking to restore macOS 12 support. I'm asking for a graceful way to stay on the last version that works on my hardware, so I'm not one reboot away from a bricked install every time Sparkle runs.

Why this isn't a duplicate of #37019 / #37070

Those are bug reports about the macOS 12 drop and were closed as "won't fix" (Chrome/security rationale). This is a feature request about the update mechanism itself, which applies to any future minimum-OS bump — not just this one. The next time the minimum OS rises, the same users will be in the same loop unless one of the above options exists.

Start by locating the Sparkle appcast and the desktop update settings or entry points. Check how minimumSystemVersion is advertised and how update preferences are handled. Done means macOS 12 users no longer receive incompatible builds, or have a supported opt-out, choice, or documented version-pinning path.