Improve bash script error handling and portability

[Copilot]

The bash scripts created in this PR lacked proper error handling and used non-portable shebangs. Scripts would fail silently or with cryptic errors when dependencies were missing or files didn't exist.

Changes

Error handling:

• Added set -euo pipefail to all scripts
• Added validation for required tools (jq, zip)
• Added validation for required files/directories before operations

Portability:

• Changed shebang from #!/usr/bin/bash to #!/usr/bin/env bash
• Fixed unset variable handling with ${1:-} pattern
• Made scripts executable with proper permissions

Code quality:

• Fixed shellcheck warnings (read -r instead of read)
• Added *.zip to .gitignore to exclude build artifacts

All scripts now fail fast with clear error messages when preconditions aren't met.

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