Add CI/CD workflows via GitHub Actions

[Copilot]

Implements automated testing, linting, and multi-platform release builds using GitHub Actions.

CI Workflow (.github/workflows/ci.yml)

Runs on push/PR to main/master/rebuild branches:

• Format Check: cargo fmt --all -- --check
• Clippy Lints: cargo clippy --all-targets --all-features
• Build: Debug and release builds
• Test: Full test suite execution

Includes cargo caching (registry, git index, build artifacts) and system dependencies installation for GUI libraries.

CD Workflow (.github/workflows/release.yml)

Triggered by version tags (v*) or manual dispatch:

• Creates GitHub release from tag
• Builds stripped binaries for Linux, Windows, macOS (x86_64)
• Uploads artifacts to release

Uses matrix strategy for parallel platform builds.

Code Changes

Fixed clippy error preventing clean builds:

// src/ui/layout.rs:843
- if shadow_alpha <= 0 {  // Error: absurd comparison for unsigned type
+ if shadow_alpha == 0 {

Applied cargo fmt to pass CI checks.

Documentation

Added development and CI/CD sections to README with build/test/release instructions.

Original prompt

implement ci/cd via github actions

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💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.

[j-cray]

@copilot add the branch rebuild to that.

[Copilot]

@copilot add the branch rebuild to that.

Added the rebuild branch to the CI workflow triggers in commit e1af483. The workflow will now run on pushes and pull requests to main, master, and rebuild branches.