docs(wiki): update documentation and SEO wording

[ThisIs-Developer]

Summary

Updates Markdown Viewer documentation and discoverability wording across the README, wiki, app metadata, desktop docs, and localized README notices.

What changed

• Rewrote wiki pages to reflect current product behavior, limitations, privacy boundaries, storage, sharing, desktop behavior, and deployment workflows.
• Updated README feature wording and ordering, including separate Live Share and Share Snapshot entries, WaveDrom as its own feature point, and a more human Development Journey section.
• Restored all title metadata to the existing secure editor title while refining non-title descriptions around browser-based Markdown editing, .md opening, live preview, sync scrolling, GFM, math, diagrams, and exports.
• Removed the phrase “local-first” from documentation and metadata in favor of clearer on-device behavior wording.
• Updated the technology stack table and desktop package description to match current implementation.

Validation

• git diff --check
• node --check script.js
• manifest.json and desktop-app/package.json JSON parse
• index.html JSON-LD parse
• Searched the changed docs/metadata for local-first / local first

Only normal Git CRLF warnings were reported.

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Project	Deployment	Actions	Updated (UTC)
markdown-viwer	Ready	Preview, Comment	Jul 5, 2026 5:36pm

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Latest commit:	846c317
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Preview URL:	https://5a85785b.markdownviewer.pages.dev
Branch Preview URL:	https://codex-update-docs-and-seo.markdownviewer.pages.dev

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