Fix CI: release grep exit code, golangci-lint v2 config version

Release pipeline crashed when no prior release existed because
grep returned exit 1 (no match) under set -e. Add || true.

golangci-lint v2 requires a version: "2" field in .golangci.yml.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.golangci.yml

@@ -1,3 +1,5 @@
+version: "2"
+
 linters:
   enable:
     - errcheck