chore(claude): add YouTrack command suite

Port create-defect, create-story, estimate-issues, fix-defect,
implement-feature and split-story commands, adapted for GitOps
(kustomize build + kubectl dry-run gates, NCI routing).
implement-feature now walks subtasks, respects blocked-by, and reports
cross-project (NCS/NCWF) tasks. Ignore .claude/worktrees.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.gitignore

@@ -109,3 +109,6 @@ fabric.properties
 # kustomization.yaml and *.yaml are tracked; raw *.yml files are not
 secrets/**/*.yml
 /scripts/sealed-secrets-key-backup.yaml
+
+# Claude Code
+/.claude/worktrees/