Add bootstrap.sh with zsh and git modules

Cross-distro (RHEL/Debian) VM setup: zsh + oh-my-zsh with a self-healing
bash fallback for environments that reset the root filesystem or hardcode
bash for new terminals (e.g. Kasm Workspaces), plus git identity and
HTTPS credential-store configuration.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

README.md

@@ -1,3 +1,18 @@
 # dotfiles
 
-Public collection of scripts and configs — incl. mcp-config/ (LiteLLM MCP gateway sync for laptops)
+Configures fresh VMs (RHEL-family or Debian-family) with a consistent
+environment. Run `./bootstrap.sh` (or curl-pipe it) to apply everything;
+each module also runs standalone and is safe to re-run.
+
+## Modules
+
+- `zsh/` — installs zsh + oh-my-zsh, drops a managed `~/.zshrc`
+  (robbyrussell theme, git plugin), and sets zsh as the login shell.
+- `git/` — sets git `user.name`/`user.email` and configures
+  `credential.helper store` (plaintext `~/.git-credentials`, 0600) for
+  HTTPS auth.
+- `mcp-config/` — shared MCP gateway config sync for laptops (LiteLLM /
+  opencode). Independent of `bootstrap.sh`; see its own README.
+
+`lib/os-detect.sh` provides shared package-manager detection (`dnf`/`yum`
+vs `apt`) used by module install scripts.