Agentic UI: Add a first-run orientation guide

[bcotrim]

Related issues

• Related to STU-2016

How AI was used in this PR

Implemented with Claude Code; Reviewed and tested manually.

Proposed Changes

Adds a first-run orientation guide to the agentic UI — a focused three-page modal that introduces the sidebar, Studio Code, and the live preview. It opens once on first arrival in the workbench and can be reopened anytime from Help ▸ Getting Started.

The copy adapts to the user:

• New vs migrating (page 1): a fresh install is welcomed to Studio; someone coming from classic Studio is reassured their sites and files carried over.
• Studio Code available vs not (pages 2–3): when chat is on, the guide teaches building by asking and the realtime preview; when it isn't — signed out, offline, or turned off in Settings → AI — it points to the site overview and the plain preview instead.

Seen-state persists (desktop app.json, browser localStorage) and is versioned, so it never nags but can be re-shown after a redesign.

Step 1	Step 2	Step 3

Testing Instructions

1. Enable the Agentic UI beta feature and open a site's workbench.
2. Choose Help ▸ Getting Started — the guide opens.
3. Page through it: Back appears from page 2, the dots stay centered, the last button (Let's go) closes it. Confirm Esc and the ✕ Skip button also close it.
4. Signed in with Studio Code on, pages 2–3 read Build by asking / See your site update in realtime.
5. Turn agentic features off in Settings → AI (or sign out), reopen from Help — pages 2–3 now read Manage your site / See your site inline.
6. Verify in both light and dark mode.

Pre-merge Checklist

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

[wpmobilebot]

📊 Performance Test Results

Comparing 13dc62f vs trunk

app-size

Metric	trunk	13dc62f	Diff	Change
App Size (Mac)	1372.96 MB	1372.98 MB	+0.02 MB	⚪ 0.0%

site-editor

Metric	trunk	13dc62f	Diff	Change
load	1083 ms	1080 ms	3 ms	⚪ 0.0%

site-startup

Metric	trunk	13dc62f	Diff	Change
siteCreation	6477 ms	6550 ms	+73 ms	🔴 1.1%
siteStartup	2391 ms	2392 ms	+1 ms	⚪ 0.0%

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Results are median values from multiple test runs.

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