#23597: fix(mac): stop Sparkle updater from offering downgrades as updates

## Problem macOS users on the latest version (2026.2.21) are prompted to "update" to an older version (2026.2.15): > **A new version of OpenClaw is available!** > OpenClaw 2026.2.15 is now available—you have 2026.2.21. Would you like to download it now? <img width="570" height="405" alt="Screenshot 2026-02-22 at 8 42 39 PM" src="https://github.com/user-attachments/assets/453a918f-8408-49a6-af56-1a577e38f8ef" /> This is a downgrade, not an upgrade. Clicking "Install Update" would roll the user back to a week-old release. ## Root cause `package-mac-app.sh` defaults `APP_BUILD` (which becomes `CFBundleVersion` / `sparkle:version`) to `git rev-list --count HEAD` — a plain commit count. For 2026.2.21 this produced `13056`. Sparkle compares versions numerically, so: ``` 13056 (2026.2.21) < 202602150 (2026.2.15) ``` Sparkle concludes 2026.2.15 is newer and offers the "update." The same class of bug previously affected 2026.2.13 (#22702). ## Fix | File | Change | |---|---| | `scripts/package-mac-app.sh` | Auto-derive `APP_BUILD` as `YYYYMMDD0` from `APP_VERSION` (e.g. `2026.2.21` → `202602210`). Git commit count is now only a fallback for non-standard version formats. No more manual `APP_BUILD` override needed at release time. | | `appcast.xml` | Correct 2026.2.21 `sparkle:version` from `13056` → `202602210` | | `test/appcast.test.ts` | Validate `sparkle:version` format for **every** appcast item (not just 2026.2.15), so CI catches mismatches immediately | This is a superset of #23292 (data-only fix) — it also addresses the build script issue that caused both #22702 and #23292. ## Test plan - [x] `vitest run test/appcast.test.ts` passes (3 items validated) - [x] Smoke-tested bash derivation: `2026.2.21 → 202602210`, `2026.12.5 → 202612050` - [ ] Verify macOS update check no longer offers downgrade Closes #22657 🤖 Generated with [Claude Code](https://claude.com/claude-code) <!-- greptile_comment --> <h3>Greptile Summary</h3> Fixes a critical macOS auto-updater bug where users on 2026.2.21 were prompted to "update" to 2026.2.15 (a downgrade). The root cause was that `sparkle:version` used git commit count (`13056`) instead of a date-based build number, causing Sparkle to compare `13056 < 202602150` and incorrectly offer the older release as an "update." The fix auto-derives `APP_BUILD` as `YYYYMMDD0` from `APP_VERSION` in `package-mac-app.sh`, corrects the 2026.2.21 appcast entry, and extends test coverage to validate all appcast items (not just 2026.2.15). This prevents future version comparison bugs. <h3>Confidence Score: 5/5</h3> - This PR is safe to merge - it fixes a critical bug with a clean, well-tested solution - The fix correctly addresses the root cause (git commit count vs date-based versioning), includes both the build script fix and data correction, and adds comprehensive test coverage to prevent regression. The bash logic is sound, preserves backward compatibility with explicit APP_BUILD overrides, and the numeric validation ensures Sparkle compatibility. - No files require special attention _{Last reviewed commit: 6ae41d7} <!-- greptile_other_comments_section --> _{(2/5) Greptile learns from your feedback when you react with thumbs up/down!} <!-- /greptile_comment -->