[SaladDay]

Why

This CI build failed while downloading the mcode-tools archive from npm: the TLS connection was reset (ECONNRESET). The download had no retry, so one temporary network failure stopped the build.

Changes

• Retry temporary connection failures, interrupted downloads, timeouts and HTTP 408/429/500/502/503/504 up to three times, with 1-second and 2-second backoff. Respect Retry-After up to 30 seconds.
• Keep the 120-second deadline per attempt and log retries with the final failure cause. Permanent errors and integrity failures still fail immediately; cache and integrity checks are preserved.
• Add regression tests for recovery, retry limits, permanent errors and corrupt archives.

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