Agentic UI: Lock the create-site WordPress version field while offline

[bcotrim]

Related issues

• Related to STU-1927
• Follow-up to Agentic UI: Make the site settings WordPress version field a dropdown #4284, which added this behavior to the site settings form

How AI was used in this PR

Implemented with Claude: ported the legacy wp-version-selector offline semantics onto the create-site form, reusing the offline support wpVersionField already gained in #4284. Code and tests reviewed by me.

Proposed Changes

The WordPress version field in the agentic UI create-site form didn't account for being offline. Because the version list is fetched over the network, going offline left the field with nothing to offer and it degraded to a free-text input — you could type any version, and only "latest" can actually be installed without a download.

• Offline, the field now locks to "latest" and is disabled, with the explanation shown as a hover tooltip — the same behavior Studio Classic's create form has, and the same the settings form got in Agentic UI: Make the site settings WordPress version field a dropdown #4284.
• The field stays a dropdown while offline instead of degrading to free text, so there's no way to type a version that can't be installed.
• A pre-seeded version is forced back to "latest" while offline — e.g. when a Blueprint suggestion asks for 6.7 — so the form can't submit something that would fail on creation.
• Online behavior is unchanged, including the existing free-text fallback when the version list can't be fetched while online.

Light	Dark

Testing Instructions

1. Launch Studio with the agentic UI and start creating a new site → expand Advanced settings.
2. While online, confirm the WordPress version field is unchanged: a dropdown with "latest" plus the available versions, and still editable.
3. Go offline (turn off Wi-Fi), then reopen the create-site form → Advanced settings.
4. The WordPress version field should be a disabled dropdown showing "latest" — not a text input. Hover it: the tooltip reads "Changing WordPress version requires an internet connection."
5. Still offline, start the flow from a Blueprint that suggests a specific version (e.g. 6.7) — the field should force back to "latest" rather than keeping the suggested version.
6. Create the site while offline and confirm it succeeds on the latest bundled version.
7. Go back online — the field should re-enable and list the fetched versions again.
8. Check the field in both light and dark color schemes.

Pre-merge Checklist

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

[wpmobilebot]

📊 Performance Test Results

Comparing f364a04 vs trunk

app-size

Metric	trunk	f364a04	Diff	Change
App Size (Mac)	1377.87 MB	1377.87 MB	+0.00 MB	⚪ 0.0%

site-editor

Metric	trunk	f364a04	Diff	Change
load	1071 ms	1098 ms	+27 ms	⚪ 0.0%

site-startup

Metric	trunk	f364a04	Diff	Change
siteCreation	6987 ms	7006 ms	+19 ms	⚪ 0.0%
siteStartup	2344 ms	2342 ms	2 ms	⚪ 0.0%

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Results are median values from multiple test runs.

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