feat: add unified versioning system

Single version for entire monorepo: <major>.<merges>.<builds>
- Merges increment on ./workflow/finish
- Builds increment via CI
- Major bumps reset counters

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

VERSION.json

@@ -0,0 +1,8 @@
+{
+  "major": 1,
+  "merges": 0,
+  "builds": 0,
+  "version": "1.0.0",
+  "lastMerge": null,
+  "lastBuild": null
+}