Use sidebar chrome color for onboarding left panel in dark mode

[sejas]

Related issues

• Fixes STU-1433

How AI was used in this PR

Claude identified the relevant Tailwind color tokens and applied dark:bg-chrome and dark:from-chrome/dark:to-chrome variants to the onboarding left panel. Changes were reviewed before committing.

Proposed Changes

This is not too critical as the default color is light, so currently users won't see the onboarding on dark mode, but it's better to keep improving the dark mode screens.

• Update the onboarding screen for dark mode by changing the left panel blue to black.

Testing Instructions

• Remove the "onboardingCompleted": true and set "colorScheme": "dark" in ~/Library/Application\ Support/Studio/appdata-v1.json
• Remove all your sites to see the onboarding screen
• Start the app with npm start
• Verify the left panel background is dark (#1E1E1E) instead of blue
• Switch to light mode and verify the left panel is still blue as before

Before	After

Pre-merge Checklist

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

[wpmobilebot]

📊 Performance Test Results

Comparing 9db63f1 vs trunk

app-size

Metric	trunk	9db63f1	Diff	Change
App Size (Mac)	1236.63 MB	1236.63 MB	0.00 MB	⚪ 0.0%

site-editor

Metric	trunk	9db63f1	Diff	Change
load	1893 ms	1934 ms	+41 ms	⚪ 0.0%

site-startup

Metric	trunk	9db63f1	Diff	Change
siteCreation	6112 ms	7116 ms	+1004 ms	🔴 16.4%
siteStartup	3937 ms	3912 ms	25 ms	⚪ 0.0%

---

Results are median values from multiple test runs.

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

[gcsecsey]

Thanks for fixing this @sejas! The updated color LGTM. 👍