docs: overhaul product documentation and localized READMEs

[ThisIs-Developer]

What changed

• audited the existing Markdown documentation against the current implementation
• reorganized the root README as a concise product overview and documentation entry point
• corrected Share Snapshot, Live Share, Docker/PWA, renderer, import-limit, privacy, and storage claims
• added focused pages for Privacy and Security, Share Snapshot, and troubleshooting
• combined the localization workflow and complete five-language terminology glossary in wiki/Localization.md
• revised the Japanese, Korean, and Simplified Chinese README files and added a Traditional Chinese README
• synchronized terminology and navigation across all five documentation entry points
• added CodeWiki and DeepWiki entry badges, the independently maintained Markdown Desk showcase, a short development journey, and the contributor gallery to all five README files
• clarified the verified combination that distinguishes Markdown Viewer and added localized, collapsible 12-entry tables of contents to all five README files
• updated the product positioning and synchronized six application, renderer, and Live Share screenshots with localized alternative text across all five README files

Why

The previous documentation contained duplicated overview content, fragile links, inconsistent translated terminology, missing privacy and retention details, and several statements that no longer matched the implementation. This change makes the codebase the source of truth and separates concise entry-point content from detailed reference pages.

User and developer impact

Users receive clearer installation, usage, sharing, privacy, security, network, troubleshooting, project-history, community, and product-positioning guidance. Collapsible contents blocks and synchronized screenshots make each README easier to navigate and understand. Contributors receive a consolidated localization workflow and terminology reference. No application logic, API, storage format, dependency, deployment configuration, or product behavior is changed.

Validation

• validated 24 Markdown files for one top-level heading, Unicode integrity, balanced fences, local paths, and anchors
• resolved 306 internal documentation links and heading anchors
• confirmed all five README entry points have matching 12-section structure, synchronized positioning, six matching screenshots, localized alternative text, language labels, and peer navigation
• confirmed all 33 previously linked external documentation URLs and images responded successfully at their validation time
• identified that all six newly added github.com/user-attachments screenshot URLs return HTTP 404 to anonymous readers even though authenticated owner requests succeed; these images require stable public URLs or repository-local copies before merge
• parsed all 14 UI locale catalogs and matched them to the 1,072-key English catalog
• confirmed the removed standalone files have no remaining documentation references
• git diff --check passed
• confirmed all 23 changed or added paths are Markdown documentation
• focused Chromium tests passed for Share Snapshot temporary-tab behavior and Private mode local-storage behavior

npm run build remains blocked by the pre-existing static-validator reference to missing functions/api/report-issue.js. This documentation-only change does not create or alter that condition.

Before merge: replace or publish the six authentication-gated README screenshot assets so they render for readers who are not signed in to GitHub.

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Project	Deployment	Actions	Updated (UTC)
markdown-viwer	Ready	Preview, Comment	Jul 27, 2026 9:18pm

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