experiment: replace landing with workshop introduction

- Added Welcome card (Before we begin) to idle state
- Reduced textarea from 10 to 6 rows
- Added reassurance text below Analyse button
- Removed redundant empty-state placeholder
- Closed Experiment 03 (Partially confirmed) in evolution log
- Added Experiment 04: Facilitated Workshop Introduction
- Added Entry Experience section to UX guidelines

.claude/ux-guidelines.md

@@ -322,3 +322,17 @@ Headings should be clean. Remove unnecessary subheadings that duplicate context.
 Cards should have consistent border radius, padding, and heading treatment across the workspace.
 
 An Investigation Map Preview should look provisional — lighter borders, muted text, subtle background — so the user knows it is a preview rather than completed content.
+
+## Entry Experience
+
+The landing page is not the investigation workspace.
+
+The landing page welcomes the user.
+
+The landing page explains what will happen.
+
+Complexity appears progressively.
+
+Users begin with observations rather than conclusions.
+
+The Confidence Engine behaves like a facilitator introducing a workshop — calm, patient, and focused on understanding before acting.