fix(P1): fix bash substring in ci-release.sh — dash doesn't support ${var:0:12}

The Gitea Actions runner uses dash as /bin/sh. ${GIT_COMMIT:0:12} is
bash-only substring substitution. dash gives 'Bad substitution' (exit 1).

Fix: use $(echo "$GIT_COMMIT" | cut -c1-12) instead.

The coreci pipeline (build+test) SUCCEEDED in the last run — the only
failure was this shell compatibility issue in the release step.

---ci---
project: orca
phase: 1
milestone: v0.16
status: execute
---/ci---

scripts/ci-release.sh

@@ -26,7 +26,7 @@ GIT_COMMIT="${GIT_COMMIT:-unknown}"
 BUILD_TIME="$(date -u +%Y-%m-%dT%H:%M:%SZ)"
 TARBALL="orca-${VERSION}-linux-amd64.tar.gz"
 
-info "building release ${VERSION} (commit ${GIT_COMMIT:0:12})..."
+info "building release ${VERSION} (commit $(echo "${GIT_COMMIT}" | cut -c1-12))..."
 
 # Build the release binary with version injection.
 LDFLAGS="-s -w \