zsh/theme.zsh: restore prezto fpath before loading skwp prompt

The skwp prompt's precmd calls git-info and ruby-info (prezto module
functions that live in ~/.zprezto/modules/{git,ruby}/functions). On
interactive shell startup, something — likely compinit's
insecure-directory pruning when parent dirs are group-writable —
strips those paths from $fpath after pmodload seeded them.

When precmd then references the autoload-declared-but-unfindable
functions, zsh fails to locate the definition file, aborts the
prompt render midway through, and zsh-syntax-highlighting latches
onto the broken half-prompt. Observed symptoms:

  prompt_skwp_precmd: git-info: function definition file not found
  prompt_skwp_precmd: ruby-info: function definition file not found
  zsh: bad math expression: operand expected at '%F{135}%n%...'
  _zsh_highlight_call_widget:2: bad math expression: operand...

Defensive re-seed: before calling 'prompt skwp', prepend the helper,
git, and ruby module function dirs to $fpath if they aren't already
present. Idempotent, cheap, and masks any upstream stripping
regardless of cause.

zsh/theme.zsh

@@ -1 +1,15 @@
+# Re-add prezto module function paths to $fpath. Some flows (compinit's
+# insecure-directory check, group-writable home dirs) can strip these,
+# which leaves skwp's precmd calling autoload-declared-but-unfindable
+# functions like git-info/ruby-info, producing
+#   "zsh: bad math expression: operand expected at '%F{135}%n%...'"
+# and cascading errors in zsh-syntax-highlighting.
+() {
+  local module dir
+  for module in helper git ruby; do
+    dir="${ZDOTDIR:-$HOME}/.zprezto/modules/$module/functions"
+    [[ -d $dir && ${fpath[(I)$dir]} -eq 0 ]] && fpath=($dir $fpath)
+  done
+}
+
 prompt skwp