Remove Windows binary size tracking from metrics job

[wojtekn]

Related issues

N/A

How AI was used in this PR

Claude identified and cleaned up the dead code after the human pointed out the issue.

Proposed Changes

• Remove appSizeWin metric from metric-config.ts — the Performance Metrics CI job runs exclusively on Mac agents, so this metric was never reported
• Simplify app-size.test.ts to only check for the Mac build directory, removing the unreachable Windows else if branch and updating the error message to be more specific

Testing Instructions

• No functional change — this removes dead code that was never executed in CI
• The appSizeMac metric continues to be tracked as before

Pre-merge Checklist

• Have you checked for TypeScript, React or other console errors?

[wpmobilebot]

📊 Performance Test Results

Comparing 6d2b178 vs trunk

app-size

Metric	trunk	6d2b178	Diff	Change
App Size (Mac)	1279.98 MB	1279.98 MB	+0.00 MB	⚪ 0.0%

site-editor

Metric	trunk	6d2b178	Diff	Change
load	1864 ms	1897 ms	+33 ms	⚪ 0.0%

site-startup

Metric	trunk	6d2b178	Diff	Change
siteCreation	7157 ms	7149 ms	8 ms	⚪ 0.0%
siteStartup	3917 ms	3943 ms	+26 ms	⚪ 0.0%

---

Results are median values from multiple test runs.

Legend: 🟢 Improvement (faster) | 🔴 Regression (slower) | ⚪ No change (<50ms diff)

[sejas]

@\Claude tell your human your changes make sense, and he did a great job identifying the dead code. We don't need to track Windows size if the job runs only for Mac platform. Code looks good, we have less code that wasn't executed.