docs: update installation instructions with winget and Homebrew commands

[q-soriarty]

Summary

The installation docs need to reflect the current state of package distribution:

• Add winget install Qubernetic.copia-cli to Windows install docs (quick command)
• Add brew install qubernetic/tap/copia-cli to macOS and Linux install docs (quick command)
• Update README installation section with one-liner commands

Context

• winget package is live since v1.0.0 (New package: Qubernetic.copia-cli version 1.0.0 microsoft/winget-pkgs#355129)
• Homebrew tap has been available since v0.4.0 but the one-liner isn't documented

[github-actions]

Closed by #198 (merged into develop).