Studio: Ensure that the blueprint cards are proportionate in the blueprints gallery

[katinthehatsite]

Related issues

Fixes STU-1853

How AI was used in this PR

It was used to make a change, although it was pretty straightforward.

Proposed Changes

This PR ensures that the blueprint cards are proportionate on the blueprints gallery page. height: 100% makes every card stretch to the tallest card in its grid row.

Before

After

Testing Instructions

• Pull the changes from this branch
• Start Studio with npm start
• Enable the Agentic UI feature flag from Studio -> Feature flags from the topbar
• Click on the New site -> Start from a blueprint option
• Scroll through the blueprints gallery and confirm that you can see the same height for each card

Pre-merge Checklist

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

[wpmobilebot]

📊 Performance Test Results

Comparing 28ca942 vs trunk

app-size

Metric	trunk	28ca942	Diff	Change
App Size (Mac)	1419.29 MB	1419.29 MB	+0.00 MB	⚪ 0.0%

site-editor

Metric	trunk	28ca942	Diff	Change
load	735 ms	725 ms	10 ms	⚪ 0.0%

site-startup

Metric	trunk	28ca942	Diff	Change
siteCreation	6491 ms	6520 ms	+29 ms	⚪ 0.0%
siteStartup	2392 ms	2393 ms	+1 ms	⚪ 0.0%

---

Results are median values from multiple test runs.

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

[wojtekn]

The code change looks clear, works as expected.