feat(core): add shared bootstrap entrypoint for plugin managers

Co-authored-by: mcornella <1441704+mcornella@users.noreply.github.com>

lib/bootstrap.zsh

@@ -0,0 +1,44 @@
+#
+# Shared Oh My Zsh bootstrap entrypoint.
+#
+# This file can be sourced by plugin managers that don't source `oh-my-zsh.sh`.
+# It is safe to source multiple times.
+#
+
+# Keep source path for callers that invoke omz_bootstrap again later.
+typeset -g _OMZ_BOOTSTRAP_SOURCE="${${(%):-%x}:a}"
+
+omz_bootstrap() {
+  # If ZSH is not defined, infer from this file location.
+  [[ -n "${ZSH:-}" ]] || export ZSH="${_OMZ_BOOTSTRAP_SOURCE:h:h}"
+
+  # Set ZSH_CUSTOM to the path where custom config files and plugins exist.
+  [[ -n "${ZSH_CUSTOM:-}" ]] || ZSH_CUSTOM="$ZSH/custom"
+
+  # Set cache directory.
+  [[ -n "${ZSH_CACHE_DIR:-}" ]] || ZSH_CACHE_DIR="$ZSH/cache"
+
+  # Ensure cache dir is writable, otherwise fallback to a HOME-based cache.
+  if [[ ! -w "$ZSH_CACHE_DIR" ]]; then
+    ZSH_CACHE_DIR="${XDG_CACHE_HOME:-$HOME/.cache}/oh-my-zsh"
+  fi
+
+  # Create cache and completions dir.
+  command mkdir -p "$ZSH_CACHE_DIR/completions"
+
+  # Add required OMZ search paths.
+  local dir
+  for dir in \
+    "$ZSH/functions" \
+    "$ZSH/completions" \
+    "$ZSH_CUSTOM/functions" \
+    "$ZSH_CUSTOM/completions" \
+    "$ZSH_CACHE_DIR/completions"; do
+    (( ${fpath[(Ie)$dir]} )) || fpath=("$dir" $fpath)
+  done
+
+  # Public signal: OMZ bootstrap has completed.
+  typeset -g OMZ_IS_BOOTSTRAPPED=true
+}
+
+omz_bootstrap "$@"