dotfiles: initial scaffold for Coder devboxes

install.sh (symlink home/* + merge-seed ~/.claude.json onboarding), gitconfig,
bash_aliases, global gitignore, inputrc, tmux.conf. Golden owns tools+starship;
this owns personal config. Secrets stay in Coder user-secrets.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

home/.config/git/ignore

@@ -0,0 +1,17 @@
+# Global gitignore (referenced by ~/.gitconfig core.excludesfile)
+# OS / editor cruft that should never land in any repo.
+.DS_Store
+Thumbs.db
+*~
+*.swp
+*.swo
+.idea/
+.vscode/
+*.log
+.env
+.env.local
+node_modules/
+__pycache__/
+*.pyc
+.venv/
+.direnv/