chore: remove vibe-coding artifacts from tracking, sync notes and obsidian config

- Untrack .claude/launch.json (Claude Code config)
- Add .claude/, .mcp.json, CLAUDE.md, and AI-generated CSVs to .gitignore
- Add _notes/ vault (architecture, API, tasks, bugs, infra docs)
- Add .obsidian/ plugin/vault config (workspace state excluded)
- Sync CHANGELOG.md

_notes/.obsidian/plugins/calendar/data.json

@@ -0,0 +1,10 @@
+{
+  "shouldConfirmBeforeCreate": true,
+  "weekStart": "locale",
+  "wordsPerDot": 250,
+  "showWeeklyNote": false,
+  "weeklyNoteFormat": "",
+  "weeklyNoteTemplate": "",
+  "weeklyNoteFolder": "",
+  "localeOverride": "system-default"
+}