feat(plugin-preview): support custom fixed iframe entries

[SoonIter]

Summary

• support customEntry in both iframe-follow and iframe-fixed modes with discriminated preview, route, and demo metadata
• expose external demo source paths and add preview-only for page-level fixed previews that should not render duplicate document content
• add a localized mobile link to the generated pure Demo page while preserving the fixed desktop device
• cover Vue fixed entries, relative imports, existing React behavior, builds, HMR, and documentation

Related Issue

N/A

Screenshots

To be added before this draft is marked ready. The new mobile fallback link and its generated Demo URL are covered by the custom-entry E2E fixture.

Checklist

• Tests updated (or not required).
• Documentation updated (or not required).

[cloudflare-workers-and-pages]

Deploying rspress-v2 with    Cloudflare Pages

Latest commit:	946e2bf
Status:	✅  Deploy successful!
Preview URL:	https://0afefeb5.rspress-v2.pages.dev
Branch Preview URL:	https://codex-plugin-preview-vue-fix.rspress-v2.pages.dev

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[github-actions]

Rsdoctor Bundle Diff Analysis

Found 5 projects in monorepo, 3 projects with changes.

📊 Quick Summary

Project	Total Size	Gzip Size	Change	Gzip Change
website_html	13.9 MB	1.9 MB	+11.7 KB (0.1%)	+1.1 KB (0.1%)
website_js	16.8 MB	2.9 MB	+12.4 KB (0.1%)	+1.3 KB (0.0%)
website_md	1.7 MB	257.0 KB	+3.6 KB (0.2%)	+686.0 B (0.3%)
auto_nav_sidebar_html	304.9 KB	60.7 KB	0	0
auto_nav_sidebar_js	525.0 KB	164.5 KB	0	0

📋 Detailed Reports (Click to expand)

📁 website_html

Path: website/doc_build/diff-rsdoctor/website_html/rsdoctor-data.json

📌 Baseline Commit: d737b7e820 | PR: #3532

Metric	Current	Baseline	Change
📊 Total Size	13.9 MB	13.9 MB	+11.7 KB (0.1%)
🗜️ Gzip Size	1.9 MB	1.9 MB	+1.1 KB (0.1%)
📄 JavaScript	0 B	0 B	0
🎨 CSS	0 B	0 B	0
🌐 HTML	13.9 MB	13.9 MB	+11.7 KB (0.1%)
📁 Other Assets	0 B	0 B	0

📦 Download Diff Report: website_html Bundle Diff

📁 website_js

Path: website/doc_build/diff-rsdoctor/website_js/rsdoctor-data.json

📌 Baseline Commit: d737b7e820 | PR: #3532

Metric	Current	Baseline	Change
📊 Total Size	16.8 MB	16.8 MB	+12.4 KB (0.1%)
🗜️ Gzip Size	2.9 MB	2.9 MB	+1.3 KB (0.0%)
📄 JavaScript	16.5 MB	16.5 MB	+12.0 KB (0.1%)
🎨 CSS	139.3 KB	138.9 KB	+382.0 B (0.3%)
🌐 HTML	0 B	0 B	0
📁 Other Assets	171.9 KB	171.9 KB	0

📦 Download Diff Report: website_js Bundle Diff

📁 website_md

Path: website/doc_build/diff-rsdoctor/website_md/rsdoctor-data.json

📌 Baseline Commit: d737b7e820 | PR: #3532

Metric	Current	Baseline	Change
📊 Total Size	1.7 MB	1.7 MB	+3.6 KB (0.2%)
🗜️ Gzip Size	257.0 KB	256.3 KB	+686.0 B (0.3%)
📄 JavaScript	0 B	0 B	0
🎨 CSS	0 B	0 B	0
🌐 HTML	0 B	0 B	0
📁 Other Assets	1.7 MB	1.7 MB	+3.6 KB (0.2%)

📦 Download Diff Report: website_md Bundle Diff

Generated by Rsdoctor GitHub Action