Agentic UI: Fix theme-aware Customize shortcuts

[shaunandrews]

Related issues

• Related to Design Exploration: Rebuild the site overview around summary cards #4462

How AI was used in this PR

AI helped separate this bug fix from the larger site-overview prototype and compare the implementation with the existing Classic UI behavior. I reviewed the narrowed diff and verified it independently.

Proposed Changes

• Make the Agentic UI resolve missing theme details through the same desktop IPC flow used by Classic Studio, so running block-theme sites show Site Editor shortcuts instead of the Customizer.
• Keep persisted theme details authoritative for stopped sites and retain Classic's Customizer fallback when theme details are unavailable.
• Show neutral placeholders while theme-dependent shortcuts are resolving, avoiding a flash of incorrect actions.

Testing Instructions

1. In the desktop Agentic UI, open a running site that uses a block theme and confirm Customize offers Site Editor, Styles, Patterns, Navigation, Templates, and Pages.
2. Open a classic-theme site and confirm Customize offers Customizer plus only the Menus and Widgets capabilities supported by that theme.
3. Stop the site and confirm its persisted theme shortcuts remain available after reopening the overview.
4. Confirm a stopped site without persisted theme details falls back to Customizer and Media Library without starting the site.
5. Check the overview in both Light and Dark appearances.

Automated verification:

• npx eslint --fix apps/ui/src/components/site-overview-view/index.test.tsx apps/ui/src/components/site-overview-view/index.tsx apps/ui/src/components/site-overview-view/style.module.css apps/ui/src/data/core/connectors/ipc/index.ts apps/ui/src/data/core/types.ts apps/ui/src/hooks/use-theme-details.ts
• npm run typecheck
• npm test -- apps/ui/src/components/site-overview-view/index.test.tsx
• npm run cli:build:ui

Pre-merge Checklist

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

[wpmobilebot]

📊 Performance Test Results

Comparing 3e1694b vs trunk

app-size

Metric	trunk	3e1694b	Diff	Change
App Size (Mac)	1403.26 MB	1403.27 MB	+0.00 MB	⚪ 0.0%

site-editor

Metric	trunk	3e1694b	Diff	Change
load	1071 ms	1047 ms	24 ms	⚪ 0.0%

site-startup

Metric	trunk	3e1694b	Diff	Change
siteCreation	7527 ms	7531 ms	+4 ms	⚪ 0.0%
siteStartup	2873 ms	2880 ms	+7 ms	⚪ 0.0%

---

Results are median values from multiple test runs.

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

[katinthehatsite]

I tested this but I had the following the issue:

• install the block theme theme and confirm the correct controls are displayed
• navigate to the site in the external browser
• install a classic theme like Twenty Thirteen
• go back to the app
• observe that the controls did not update
• try using the controls
• observe the error:

• restart the site
• observe the correct controls
• with the classic UI, it was not necessary to restart the site