feat(shell): create cached-eval helper to improve shell startup speed.

zshenv

@@ -74,6 +74,54 @@ source-if-exists() {
   fi
 }
 
+# cached-eval executes a command with arguments and caches the output. On
+# subsequent calls, if the source file has not changed, the output is sourced
+# from the cache instead of re-executing the command. This optimizes performance
+# for commands that are costly to execute but result in the same output unless
+# their source files change.
+#
+# Arguments:
+#
+#   $1 - source_file: The path to the source file that the command depends on.
+#                     If this file is newer than the cache, the command is
+#                     re-executed and the cache is updated.
+#   $2 - cmd:         The command to execute.
+#   $@ - args:        Additional arguments to pass to the command.
+#
+# Example usage:
+#
+#     cached-eval "$(command -v direnv)" direnv hook zsh
+#     cached-eval "$(command -v mise)" mise activate zsh
+#
+# The above commands will cache the output of `direnv hook zsh` and `mise
+# activate zsh` respectively. If the source file is newer than the cache, the
+# command is re-executed and cache is updated.
+cached-eval() {
+  local source_file="$1"
+  local cmd="$2"
+  shift 2
+  local args="$@"
+  local full_cmd="$cmd $args"
+  local cache_dir="${ZSH_CACHED_EVAL_DIR:-$HOME/.local/share/zsh/cached-eval}"
+
+  if [[ -z "$(command -v "$cmd")" ]]; then
+     echo "cached-eval: Command not found: $cmd" >&2
+     return 1
+  fi
+
+  local cache_hash="$(echo -n "$full_cmd" | md5sum | awk '{print $1}')"
+  local cache_file="${cache_dir}/$(basename "$cmd")_${cache_hash}.zsh"
+
+  if [[ ! -f "$cache_file" || "$source_file" -nt "$cache_file" ]]; then
+    mkdir -p "$cache_dir"
+    echo "cached-eval: Updating cache for: $full_cmd --> $cache_file" >&2
+    echo -e "#\n# Generated by cached-eval: $full_cmd\n#\n" >| "$cache_file"
+    eval "$full_cmd" >>| "$cache_file"
+  fi
+
+  source "$cache_file"
+}
+
 # ==============================================================================
 # System Environment Setup
 # ==============================================================================
@@ -98,6 +146,7 @@ fi
 
 export DOTZSH_SITEFUNS="$DOTZSH/site-functions"
 export ZSH_COMPLETIONS="$HOME/.local/share/zsh/completions"
+export ZSH_CACHED_EVAL_DIR="$HOME/.local/share/zsh/cached-eval"
 
 # Ensure basic systems paths are in desired order
 path_prepend "/bin"
@@ -129,7 +178,7 @@ fi
 
 # Homebrew on Apple Silicon
 if [ -f "/opt/homebrew/bin/brew" ]; then
-  eval "$(/opt/homebrew/bin/brew shellenv)"
+  cached-eval /opt/homebrew/bin/brew /opt/homebrew/bin/brew shellenv
 fi
 
 if command-exists brew; then