Studio: New site form can be submitted with incorrect values using enter key

[katinthehatsite]

Related issues

Fixes https://linear.app/a8c/issue/STU-1490/new-site-form-can-be-submitted-with-incorrect-values-using-enter-key

How AI was used in this PR

Not used

Proposed Changes

This PR ensures that the site creation form can not be submitted with the Enter key when the site name is empty or when there are validation errors.

Testing Instructions

• Pull the changes from this branch
• Start Studio with npm start
• Click on the Add site
• Once the site form opens, remove the site name
• Press the Enter key
• Confirm that the site form can not be submitted

Pre-merge Checklist

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

[wpmobilebot]

📊 Performance Test Results

Comparing 33d3d55 vs trunk

app-size

Metric	trunk	33d3d55	Diff	Change
App Size (Mac)	1271.61 MB	1271.61 MB	+0.00 MB	⚪ 0.0%

site-editor

Metric	trunk	33d3d55	Diff	Change
load	1625 ms	1884 ms	+259 ms	🔴 15.9%

site-startup

Metric	trunk	33d3d55	Diff	Change
siteCreation	8175 ms	8170 ms	5 ms	⚪ 0.0%
siteStartup	4842 ms	4840 ms	2 ms	⚪ 0.0%

---

Results are median values from multiple test runs.

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

[epeicher]

Thanks @katinthehatsite! This works as described, but should we also disable the Add site button when the name is empty? Alternatively, I think we can remove the siteName.trim() condition as the site name is correctly inferred from the folder name. What do you think?

Site can be added with empty site name in the form	The site name is populated from the folder

[katinthehatsite]

@epeicher I added the empty site name to the list of errors to be consistent with how other errors work

[epeicher]

Thanks @katinthehatsite for addressing the comments! Now I can see that the Add site button is disabled when deleting the site name. Also, I am not able to create the site by pressing Enter when there are errors. LGTM!