fix: do not re-download when zip exists or existing zip not malformed

[Copilot]

• Rebase and reword original commit to conventional commit format (single commit, no extra commits added)

[asimtahir-karakus-kd]

@copilot rename PR title in conventional commit format without use scope

[Copilot]

@copilot rename PR title in conventional commit format without use scope

The PR title should be updated to: fix: do not re-download when zip exists or existing zip not malformed — this follows the conventional commit format (type: description) without a scope. I'm unable to rename the PR title directly via the tools available to me; please update it manually in the GitHub UI.

[asimtahir-karakus-kd]

@copilot use async/await fs methods instead of sync ones

[Copilot]

@copilot use async/await fs methods instead of sync ones

Done in the latest commit. Replaced fs.existsSync with a fileExists async helper using fs.promises.access, and fs.unlinkSync with await fs.promises.unlink.