perf(zsh): cache tool init, lazy-load, remove plugins

Startup: 150ms → 40ms (native), projected 10-30s → <1s (iSH)

- Cache mise/fzf/zoxide init output keyed on binary mtime
- zcompile all sourced files to bytecode at install time
- Lazy-load compinit (first Tab), fzf+widgets (first keystroke)
- Remove autosuggestions and syntax-highlighting plugins
- Switch mise to shims mode (no per-prompt hook)
- Conditional mkdir (skip if dirs exist)
- Remove TRAPINT/flash handler, cache session info
- Eliminate per-prompt subshell forks (REPLY pattern)

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

install.d/23-stow.sh

@@ -23,8 +23,6 @@ if ! command -v stow &> /dev/null; then
     esac
 fi
 
-stow --version | log_quote
-
 root_dir=${DOTFILES:-$(dirname "$(dirname "$(dirname "$(realpath "$0")")")")}
 
 rm -f "$HOME/.bash_profile"
@@ -49,5 +47,18 @@ fi
 # Bust PATH cache to force rebuild with new profile
 rm -f "${XDG_CACHE_HOME:-$HOME/.cache}/dots/path"
 
-log_pass "stow linked"
+# Compile zsh dotfiles for faster shell startup
+if command -v zsh &>/dev/null; then
+    zsh -c '
+        for f in ~/.zsh/*.zsh ~/.aliases ~/.profile(N); do
+            [[ $f.zwc -nt $f ]] || zcompile "$f" 2>/dev/null
+        done
+    '
+fi
+
+# Bust tool init caches so they regenerate with new PATH/tools
+rm -f "${XDG_CACHE_HOME:-$HOME/.cache}"/dots/{fzf,mise,zoxide}.zsh{,.zwc}
+
+log_pass "stow linked"
+stow --version | log_quote