chore: bootstrap nib project

Go module init, deps (cobra, chi, modernc sqlite, ulid, clipboard),
minimal main.go placeholder, CLAUDE.md with conventions.

.gitignore

@@ -0,0 +1,37 @@
+# Binary
+nib
+
+# Database
+*.db
+*.db-wal
+*.db-shm
+
+# nib data directory
+.nib/
+
+# IDE
+.idea
+.idea/
+.vscode
+.vscode/
+*.swp
+*.swo
+*~
+
+# OS
+.DS_Store
+Thumbs.db
+
+# Spec (not shipped)
+nib-unified-spec.md
+
+# Shell/profile dotfiles (host artifacts)
+.bash_profile
+.bashrc
+.profile
+.zprofile
+.zshrc
+.gitconfig
+.gitmodules
+.ripgreprc
+.mcp.json