* feat(skills): add retry mechanism for HTTP requests
Implement a retry mechanism with exponential backoff for HTTP requests in the skill installer. This improves reliability when fetching skills from GitHub by automatically retrying failed requests up to 3 times.
Add comprehensive tests to verify retry behavior under different scenarios including success on different attempts and proper delay between retries.
* fix: improve http request retry logic with status code checks
Add shouldRetry helper function to determine retryable status codes.
Close response body between retry attempts and break early for non-retryable status codes.
* refactor: remove unused BuiltinSkill struct
The struct was not being used anywhere in the codebase, so it's safe to remove it to reduce clutter and improve maintainability.
* refactor(http): move retry logic to utils package
Extract HTTP retry functionality from skills package to utils for better reusability
Add context-aware sleep function and comprehensive tests
* refactor(http): extract retry delay unit to variable
Extract hardcoded retry delay unit to a variable for better testability and flexibility. Update tests to use milliseconds for faster execution while maintaining the same behavior.
* test(http_retry): remove t.Parallel from test cases
* test(http_retry): remove redundant test cases for retry success
The removed test cases for success on second and third attempts were redundant since the retry logic is already covered by other tests. This simplifies the test suite while maintaining coverage.
