Gh.failedLog is silent when gh exits non-zero #26

Gh.failedLog (src/main/java/dispatch/workspace/Gh.java:127-129) returns "" when gh run view --log-failed exits non-zero, with no log line. A CI fix run then gets no failed log, and nobody can tell from the logs whether the log had expired, gh was not authenticated, or the call timed out.

Fix: log a WARN with the exit code and stderr tail before returning "" (the empty return itself is fine: the fix run still has the check name).

Confirmed by reading the code on 2c19448.