The write-guard's matcher regex never matched the actual tool names
(createUserStory/createTask/createIssue, not user_story_create etc.), so
the metadata guard has never actually fired. It also checked for
assigned_to/milestone fields that don't exist on any create tool's
schema, which would have denied every create once the matcher was fixed.
Guard now validates only the tag contract (area/source/target), covers
the batch-create tools per item, and SKILL.md documents the real
follow-up calls (assignIssue/assignUserStoryToSprint/addIssueToSprint)
needed to set owner and sprint after creation.
