fix(download): enforce three total attempts

[rldyourmnd]

Summary

• change reviewed curl paths from five retries to two retries after the initial request
• establish exactly three total download attempts across tool cache, benchmark bootstrap, and runner metadata bootstrap
• leave provider state retries and service readiness polling under their separate typed deadlines
• release provider .78 for the metadata bootstrap change

Validation

• no --retry 3..9 remains in reviewed shell/Go paths
• focused repository/provider tests
• make verify

Implements the owner retry contract: initial failure, retry, retry, then terminal logged failure.