dx: compact storybook PR comment to single-line header (#9078)

## Summary

Compact the Storybook build status PR comment to a single-line header
with collapsible details, matching the approach from #8677.

## Changes

- **Starting**: Collapsed from multi-line with build steps to `## 🎨
Storybook: ⏳ Building...`
- **Completed (success)**: `## 🎨 Storybook: ✅ Built — [View
Storybook](url)` with timestamp/links in `<details>`
- **Completed (failure)**: `## 🎨 Storybook: ❌ Failed` with details
collapsed
- Removed version-bump branch check (starting comment no longer varies
by branch type)

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-9078-dx-compact-storybook-PR-comment-to-single-line-header-30f6d73d365081b98666c48a94542b70)
by [Unito](https://www.unito.io)

.github/workflows/ci-tests-storybook.yaml

@@ -24,8 +24,7 @@ jobs:
           ./scripts/cicd/pr-storybook-deploy-and-comment.sh \
             "${{ github.event.pull_request.number }}" \
             "${{ github.head_ref }}" \
-            "starting" \
-            "$(date -u '+%m/%d/%Y, %I:%M:%S %p')"
+            "starting"
 
   # Build Storybook for all PRs (free Cloudflare deployment)
   storybook-build: