Improve repository discoverability

[CCDawn]

What changed

• Rebuilds the Chinese and English repository landing pages around an immediate Windows EXE download path, product proof, feature matrix, trust boundaries, FAQ, and developer entry points.
• Moves the large character preset and eight-image concept gallery into dedicated bilingual Showcase pages without deleting them.
• Adds a 1280×640 social preview asset built from a real Codex Dream Skin screenshot, plus its reproducible SVG source.
• Rewrites the reusable promotion copy around the current repository, Windows manager, supported formats, and safe public messaging.

Why

The previous landing page led with sponsorship and a character preset, while the new self-contained Windows manager and direct release download appeared too late. The repository description also framed the project primarily as compatibility fixes. This change makes the product, download, proof, and safety model understandable in the first screen while retaining the existing showcase and sponsor content deeper in the documentation.

External repository metadata already updated

• Description: Codex desktop themes and live wallpapers
• Homepage: latest release
• Topics expanded for Codex, live wallpaper, desktop customization, Windows, macOS, WinForms, Electron, and developer tools

Validation

• All local Markdown and HTML-relative links in README/Showcase resolve
• Social preview verified at 1280×640
• git diff --check
• powershell.exe -NoProfile -ExecutionPolicy Bypass -File windows/tests/run-tests.ps1