Polish open-source project presentation

[everettjf]

What changed

• redesign the English and Chinese README headers with the app icon, release/test/platform badges, product links, and full-width screenshot showcases
• add a macOS core-test workflow for pushes and pull requests
• add structured bug and feature issue forms, a pull request checklist, release-note categories, and code ownership
• add contribution, support, security, and conduct policies

Why

The repository already has strong comparison correctness and performance work, but its public landing page and contributor workflow did not communicate that quality. These changes make the project easier to evaluate, build, test, contribute to, and report issues against.

Validation

• bash macos/Tests/run-tests.sh — all 45 focused checks and 300 randomized shortest-edit-script cases passed
• parsed every .github/**/*.yml file successfully
• git diff --cached --check
• visually inspected both 2560×1600 README screenshots

Note

A license is intentionally not included because the owner still needs to choose the legal terms (for example MIT or Apache-2.0).