- Add nil-check for version regex match with informative error message
- Use Shellwords.escape() to safely handle tag names in shell commands
- Fix PKG_CONFIG_PATH handling to properly escape paths with special characters
- Improves robustness against malformed configuration or injection attacks

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

**Critical Fixes:**
- Add null pointer checks in callback for input validation
- Check for integer overflow in callback size calculation
- Add CURL handle validation after curl_easy_init()
- Use std::call_once for thread-safe CURL global initialization
- Check curl_easy_perform() return value and report errors
- Validate JSON parse errors with HasParseError()
- Add null checks for curl_easy_escape() allocations
- Remove unused includes and 'using namespace' directives
- Add public setTimeout() method for configurable timeouts

**Improvements:**
- Use std::ostringstream for efficient URL parameter encoding
- Replace static bool with std::once_flag for thread safety
- Return meaningful error messages on failures
- Add exception safety in callback function
- Proper cleanup of CURL resources on all error paths

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>