fix: harden error handling and shell-agnostic mise activation

- Guard x-path call to prevent PATH clobber when missing
- Make husky init.sh use shell-agnostic mise activate --shims
- Add fail-fast to Tier 2 install steps in dfm install all
- Check brew update exit status before reporting success
- Always run mise install during reset_nvim (handles bootstrap)
- Use double-bracket conditional in cleanup script

config/exports

@@ -20,8 +20,10 @@
 
 # Bootstrap: ensure local/bin is on PATH so x-path is available
 PATH="$DOTFILES/local/bin:$PATH"
-# Use x-path to deduplicate PATH entries
-PATH="$(x-path prepend "$XDG_BIN_HOME" "$DOTFILES/local/bin" "/opt/homebrew/bin" "/usr/local/bin")"
+# Use x-path to deduplicate PATH entries (only if x-path is available)
+if command -v x-path &> /dev/null; then
+  PATH="$(x-path prepend "$XDG_BIN_HOME" "$DOTFILES/local/bin" "/opt/homebrew/bin" "/usr/local/bin")"
+fi
 export PATH
 
 if ! command -v msg &> /dev/null; then