fix(lint): add version field to golangci-lint config

Add required version: 2 field to .golangci.yml for compatibility with
golangci-lint v2.0+. Without this field, the linter fails with
'unsupported version of the configuration' error.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: platinummonkey

.golangci.yml

@@ -1,6 +1,9 @@
 # golangci-lint configuration for pup
 # https://golangci-lint.run/usage/configuration/
 
+# Specify config format version (required in v2.0+)
+version: 2
+
 run:
   timeout: 5m
   tests: true