fix: staticcheck S1016 struct conversion + Helm with/else-if parse error

- Use type conversion DigestStatusCount(c) instead of struct literal
- Replace with...else-if (invalid in Go templates) with if...else-if chain
- Add *.bak and cmd/agent/*.key/*.pem to .gitignore

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

.gitignore

@@ -43,6 +43,11 @@ vendor/
 tmp/
 temp/
 *.log
+*.bak
+
+# Private keys (agent-generated, never commit)
+cmd/agent/*.key
+cmd/agent/*.pem
 
 # Database
 *.db