fix(taiga-auto-sync): match real Taiga MCP tool names and drop impossible owner/sprint checks

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.

plugins/taiga-auto-sync/hooks/claude-codex-hooks.json

@@ -1,7 +1,7 @@
 {
   "hooks": {
     "PreToolUse": [{
-      "matcher": "^mcp__taiga__(user_story|task|issue)_create$",
+      "matcher": "^mcp__taiga__(createUserStory|createTask|createIssue|batchCreateUserStories|batchCreateTasks|batchCreateIssues)$",
       "hooks": [{
         "type": "command",
         "command": "python3 \"${CLAUDE_PLUGIN_ROOT}/hooks/taiga-write-guard.py\"",