fix(ci3): GITHUB_REPOSITORY unbound when running ci.sh/bootstrap_ec2 locally

The repo-scoped instance name added `repo=${GITHUB_REPOSITORY##*/}` followed by
`repo=${repo:-aztec-packages}`. Under `set -u` (set by ci3/source), the `##*/`
expansion on an unset GITHUB_REPOSITORY aborts before the default on the next line
applies — so any local `./ci.sh <cmd>` fails with "GITHUB_REPOSITORY: unbound
variable". It only surfaced locally; CI always has GITHUB_REPOSITORY set.

Default first, then strip: `repo=${GITHUB_REPOSITORY:-aztec-packages}; repo=${repo##*/}`.
Same fix in ci.sh and ci3/bootstrap_ec2.

Author: charlielye

ci.sh

@@ -55,8 +55,8 @@ function print_usage {
 
 # Keep this in sync with bootstrap_ec2's instance_name scheme (repo-scoped) so the
 # shell/kill/get-ip helpers find instances launched by a CI run for this repo.
-repo=${GITHUB_REPOSITORY##*/}
-repo=${repo:-aztec-packages}
+repo=${GITHUB_REPOSITORY:-aztec-packages}
+repo=${repo##*/}
 instance_name=${INSTANCE_NAME:-${repo}_$(echo -n "$BRANCH" | tr -c 'a-zA-Z0-9-' '_')_${arch}}
 [ -n "${INSTANCE_POSTFIX:-}" ] && instance_name+="_$INSTANCE_POSTFIX"
 

ci3/bootstrap_ec2

@@ -71,8 +71,8 @@ fi
 # the same tag/ref concurrently under the same role, and must not reap each
 # other's instances. The key stays stable across re-runs within a repo, so the
 # orphan cleanup still works.
-repo=${GITHUB_REPOSITORY##*/}
-repo=${repo:-aztec-packages}
+repo=${GITHUB_REPOSITORY:-aztec-packages}
+repo=${repo##*/}
 if [[ "$REF_NAME" =~ ^gh-readonly-queue/.*(pr-[0-9]+) ]]; then
   instance_name="${repo}_${BASH_REMATCH[1]}_$arch"
 else