Initial commit: positioning, license, project scaffold

Arboretum — self-hosted web dashboard for git worktrees and the Claude
Code sessions running on them. README states the positioning vs
GitKraken Agent Mode, Happy/CloudCLI and Anthropic Remote Control, the
security model (localhost-first + Tailscale), and the Claude usage note.

.gitignore

@@ -0,0 +1,10 @@
+node_modules/
+dist/
+*.log
+.env
+.env.*
+*.db
+*.db-*
+.DS_Store
+spikes/**/tmp/
+spikes/**/captures/