[codex] Optimize SEO performance and security hardening

[ThisIs-Developer]

PR Title

[Phase 1 | Phase 2 | Phase 3]: Improve SEO metadata, load path, CSP hardening, and MathJax lifecycle cleanup

Investigation Summary

• Current State: Static Markdown Viewer app with existing canonical, hreflang, JSON-LD, deferred CDN libraries, SRI, service worker caching, DOMPurify sanitization, worker rendering, and cleanup for STL/object URL resources.
• Issues Identified:
  • No Content Security Policy was present.
  • One inline onload handler blocked strong CSP adoption.
  • Default Markdown was stored in a non-executed <script type="text/markdown">.
  • Bottom bootstrap.bundle and script.js were not deferred.
  • JSON-LD lacked feature/version detail.
  • PWA manifest lacked stable id, scope, and categories.
  • MathJax could typeset before ready and could race against preview DOM replacement.
• Optimization Opportunities: Tighten metadata, remove inline handler/script-like content, defer scripts, add CSP, and serialize/clear MathJax rendering state.

Changes Made

Phase 1: SEO Optimization

• Updated title/Open Graph/Twitter title to target secure online Markdown editor/previewer search intent.
• Added max-image-preview:large, application-name, theme-color, og:site_name, JSON-LD softwareVersion, and a 5-item featureList.
• Added manifest id, scope, and categories.
  Verification: Static comparison: JSON-LD feature count 0 -> 5; manifest identity/scope/categories absent -> present.

Phase 2: Website Performance

• Deferred bottom Bootstrap/app scripts.
• Removed the Bootstrap Icons inline preload onload, replacing it with a normal stylesheet link so CSP can block inline script execution.
• Converted default Markdown storage from <script type="text/markdown"> to hidden <textarea>.
  Verification: Static comparison: deferred scripts 6 -> 8, inline onload handlers 1 -> 0, text-markdown script tags 1 -> 0; local post-change app-ready sample averaged 1082 ms across 5 reloads.

Phase 3: Memory Management & Security

• Added a CSP meta policy restricting script/connect/style/font/img/media/worker sources while preserving current CDN, GitHub import, diagram, and map workflows.
• Added a SHA-256 hash for the inline JSON-LD block instead of allowing arbitrary inline scripts.
• Added MathJax readiness serialization, connected-node filtering, preview cleanup via typesetClear, and removed the redundant AMS loader request.
  Verification: Fresh browser interaction inserted math Markdown, rendered 2 MathJax containers, preview state stayed ready, and fresh warning/error logs were empty.

Verification Results

• No existing functionality broken: editor and preview rendered Markdown/math successfully.
• Performance path improved: deferred scripts 6 -> 8, inline handler count 1 -> 0.
• Security hardening added: CSP present, no arbitrary inline script allowance; no CVE-specific dependency change.
• SEO improvements confirmed: title/robots/JSON-LD/manifest metadata updated.
• Code review completed: diff limited to index.html, manifest.json, script.js.

Additional checks:

• node --check script.js
• node --check preview-worker.js
• manifest.json parsed successfully
• Browser verification on http://127.0.0.1:8080

Conclusion

The app already had good sanitizer/SRI/caching foundations, but improvements were necessary. This PR adds measurable SEO/security/performance hardening while keeping the changes targeted and reversible.

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Project	Deployment	Actions	Updated (UTC)
markdown-viwer	Ready	Preview, Comment	Jun 25, 2026 11:59am

[cloudflare-workers-and-pages]

Deploying markdown-viewer with    Cloudflare Pages

Latest commit:	fd3b18d
Status:	✅  Deploy successful!
Preview URL:	https://044efe81.markdown-viewer.pages.dev
Branch Preview URL:	https://codex-seo-performance-securi.markdown-viewer.pages.dev

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[cloudflare-workers-and-pages]

Deploying markdownviewer with    Cloudflare Pages

Latest commit:	fd3b18d
Status:	✅  Deploy successful!
Preview URL:	https://dec3449c.markdownviewer.pages.dev
Branch Preview URL:	https://codex-seo-performance-securi.markdownviewer.pages.dev

View logs

[ThisIs-Developer]

Update: Inline LaTeX duplicate render fix

Added a follow-up fix for the initial paste lifecycle bug reported with:

## 1. Basic Arithmetic & Algebra

Inline: The quadratic formula is $x = \dfrac{-b \pm \sqrt{b^2 - 4ac}}{2a}$ and it has two roots.

Root Cause

The preview math pipeline could re-process already-rendered MathJax output during the initial paste path. This happened because broad preview-root MathJax targets were reused during forced/no-op post-processing, and MathJax startup/loading was not centralized enough to avoid overlapping lifecycle work.

Fix

• Reuse in-flight lazy script/style loads instead of creating duplicate loader promises.
• Centralize MathJax configuration/loading through ensureMathJaxReady().
• Disable MathJax startup auto-typesetting so only the app-controlled preview path typesets.
• Invalidate pending MathJax work when preview DOM is replaced.
• Target only text blocks that still contain raw TeX delimiters (p, li, .math-block, etc.) instead of handing the whole preview root back to MathJax.

Verification

• Reproduced the bug before the final fix: initial paste produced paragraphMjxCount: 2 and duplicated formula text.
• Verified after the fix on a fresh local origin:
  • Immediately after paste: paragraphMjxCount: 1, previewMjxCount: 1
  • After reload: paragraphMjxCount: 1, previewMjxCount: 1
  • Fresh warning/error logs: empty
• Checks passed:
  • node --check script.js
  • node --check preview-worker.js
  • manifest.json parse check