fix(ci): exclude SC2034/SC2154 from shellcheck

SC2034 (appears unused) fires on variables defined in sourced library
files (defaults.sh) that are consumed by the sourcing scripts. SC2154
(referenced but not assigned) fires on eval-assigned variables used
for bash 3.2 nameref compatibility. Both are false positives in our
source-based architecture.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: kaman1

.github/workflows/test.yml

@@ -45,4 +45,4 @@ jobs:
           set -e
           # Lint every bash script in scripts/bash/ and tests/
           find scripts/bash tests -name "*.sh" -type f -print0 \
-            | xargs -0 shellcheck --severity=warning --exclude=SC1091,SC2086,SC2155
+            | xargs -0 shellcheck --severity=warning --exclude=SC1091,SC2034,SC2086,SC2154,SC2155