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>

git/install.sh

@@ -0,0 +1,21 @@
+#!/usr/bin/env sh
+# git/install.sh — configure git identity + HTTPS credential storage.
+# Idempotent: safe to re-run.
+set -eu
+
+say() { printf '%s\n' "$*" >&2; }
+
+GIT_NAME="Nic O'Connor"
+GIT_EMAIL="nic.oconnor@gmail.com"
+
+git config --global user.name "$GIT_NAME"
+git config --global user.email "$GIT_EMAIL"
+say "git identity: $GIT_NAME <$GIT_EMAIL>"
+
+# Plaintext credential cache in $HOME (survives container/VM rebuilds that
+# wipe everything outside $HOME). Git creates ~/.git-credentials with 0600
+# the first time a credential is saved.
+git config --global credential.helper store
+say "credential.helper = store (~/.git-credentials, created on first auth)"
+
+say "Done. On the next HTTPS push/pull to a new host, git prompts once and caches the credential in ~/.git-credentials."