The RunRequest proto already has an optional `sha` field, but `depot ci
run` never populated it. This meant the API compile step cloned at the
default branch tip, missing any local action files that only exist on
the feature branch.

Now resolves `git rev-parse HEAD` and sends it. If the commit isn't
pushed to the remote, the API clone fails with a clear "ref not found"
error — an improvement over the previous silent ENOENT on action files.

Refs: DEP-3914, DEP-3915
Made-with: Cursor

bot reviewed Mar 25, 2026

Move HEAD SHA print statement to before the visual separator line to group it with other pre-request diagnostic information (Repo, Jobs, etc.) rather than appearing after the separator where it looks like response data.

Applied via @cursor push command