Pass 2 elements to SetRetryBackoff (matching maxRetryAttempts-1 = 2)
and check the error return. Previously passing 1 element silently
failed, causing tests to fall back to default {1s, 2s} backoffs.
Fixes self-review finding: 429Retry tests now run in <10ms instead
of ~1s.
Implement FileReader conformance on the GitHub client: GetFileContent,
ListContents, path helpers, base64 decode. Includes compile-time
conformance checks for both PRReader and FileReader.
Requires PR B (#102). Part 3 of 3 for #80.
claw
aweiker