fix(shell): use single ~/.config/zsh/local.zsh for machine local

Replace the local/ directory of split env/login/interactive files with
one always-on local.zsh sourced from .zshenv. Deploy migrates old
fragments and never overwrites local.zsh.

deploy.sh

@@ -1,12 +1,12 @@
 #!/usr/bin/env bash
 # Install managed easyzsh shell layout into a home directory.
 # Overwrites: ~/.zshenv ~/.zshrc ~/.zprofile ~/.config/zsh/{env,interactive,login}
-# Never overwrites: ~/.config/zsh/local/**  ~/.config/zshrc/**  ~/.local/bin/**
+# Never overwrites: ~/.config/zsh/local.zsh  ~/.config/zshrc/**  ~/.local/bin/**
 #
 # Usage:
 #   ./deploy.sh
 #   ./deploy.sh --home /path/to/home
-#   ./deploy.sh --migrate-zprofile   # move existing ~/.zprofile body into login.local
+#   ./deploy.sh --migrate-zprofile   # fold pre-easyzsh ~/.zprofile into local.zsh
 
 set -euo pipefail
 
@@ -41,6 +41,7 @@ if [[ ! -d "$TARGET_HOME" ]]; then
 fi
 
 ZSH_CFG="${TARGET_HOME}/.config/zsh"
+LOCAL_ZSH="${ZSH_CFG}/local.zsh"
 ts=$(date +%Y%m%d-%H%M%S)
 
 backup_file() {
@@ -51,49 +52,83 @@ backup_file() {
   fi
 }
 
+file_has_content() {
+  [[ -f "$1" ]] && grep -q '[^[:space:]]' "$1"
+}
+
 echo "Deploying easyzsh managed shell layout into $TARGET_HOME"
 
 mkdir -p \
   "${ZSH_CFG}/env" \
   "${ZSH_CFG}/interactive" \
   "${ZSH_CFG}/login" \
-  "${ZSH_CFG}/local" \
   "${TARGET_HOME}/.config/zshrc" \
   "${TARGET_HOME}/.cache/zsh" \
   "${TARGET_HOME}/.local/bin"
 
-# Migrate legacy early env if present and new path missing.
-if [[ -f "${TARGET_HOME}/.config/zshenv.local" && ! -f "${ZSH_CFG}/local/env.local.zsh" ]]; then
-  cp -Pp "${TARGET_HOME}/.config/zshenv.local" "${ZSH_CFG}/local/env.local.zsh"
-  echo "Migrated ~/.config/zshenv.local -> ~/.config/zsh/local/env.local.zsh"
+# Migrate split local/* and legacy paths into ~/.config/zsh/local.zsh once.
+if [[ ! -f "$LOCAL_ZSH" ]]; then
+  tmp=$(mktemp)
+  : >"$tmp"
+  if file_has_content "${TARGET_HOME}/.config/zshenv.local"; then
+    cat "${TARGET_HOME}/.config/zshenv.local" >>"$tmp"
+    printf '\n' >>"$tmp"
+  fi
+  if [[ -d "${ZSH_CFG}/local" ]]; then
+    for part in env.local.zsh login.local.zsh interactive.local.zsh; do
+      if file_has_content "${ZSH_CFG}/local/${part}"; then
+        cat "${ZSH_CFG}/local/${part}" >>"$tmp"
+        printf '\n' >>"$tmp"
+      fi
+    done
+  fi
+  if file_has_content "$tmp"; then
+    # De-dup consecutive identical non-empty lines lightly by collapsing exact file repeats later if needed.
+    cp "$tmp" "$LOCAL_ZSH"
+    echo "Migrated machine-local fragments -> ~/.config/zsh/local.zsh"
+  fi
+  rm -f "$tmp"
 fi
 
-# Optionally migrate existing zprofile body into login.local (strip redundant PATH).
-if [[ "$MIGRATE_ZPROFILE" -eq 1 ]]; then
-  if [[ -f "${TARGET_HOME}/.zprofile" && ! -f "${ZSH_CFG}/local/login.local.zsh" ]]; then
-    # Drop easyzsh stub lines and pipx ~/.local/bin PATH (now owned by env/00-path.zsh).
+# After migration (or if local.zsh already exists), drop obsolete split files.
+if [[ -d "${ZSH_CFG}/local" ]]; then
+  rm -f \
+    "${ZSH_CFG}/local/env.local.zsh" \
+    "${ZSH_CFG}/local/login.local.zsh" \
+    "${ZSH_CFG}/local/interactive.local.zsh" \
+    "${ZSH_CFG}/local/env.local.zsh.example" \
+    "${ZSH_CFG}/local/login.local.zsh.example" \
+    "${ZSH_CFG}/local/interactive.local.zsh.example"
+  rmdir "${ZSH_CFG}/local" 2>/dev/null || true
+fi
+
+# Fold a pre-easyzsh ~/.zprofile into local.zsh. Skip if already an easyzsh stub.
+if [[ "$MIGRATE_ZPROFILE" -eq 1 && -f "${TARGET_HOME}/.zprofile" ]]; then
+  if grep -Fq 'easyzsh stub' "${TARGET_HOME}/.zprofile"; then
+    echo "Skipping zprofile migration: already an easyzsh stub"
+  elif [[ ! -f "$LOCAL_ZSH" ]]; then
+    zprofile_extract=$(mktemp)
     awk '
-      /^# easyzsh stub/ { next }
-      /^EASYZSH_HOME=/ { next }
-      /for _easyzsh_f in/ { skip=1 }
-      skip && /unset _easyzsh_f/ { skip=0; next }
-      skip { next }
-      /login\.local\.zsh/ { next }
       /Created by `pipx`/ { skip_pipx=1; next }
       skip_pipx && /local\/bin/ { skip_pipx=0; next }
       skip_pipx { next }
       { print }
-    ' "${TARGET_HOME}/.zprofile" > "${ZSH_CFG}/local/login.local.zsh"
-    # Trim trailing blank lines noise if file became empty-ish
-    if ! grep -q '[^[:space:]]' "${ZSH_CFG}/local/login.local.zsh"; then
-      rm -f "${ZSH_CFG}/local/login.local.zsh"
-      echo "Existing .zprofile had no login-local content after migration"
-    else
-      echo "Migrated ~/.zprofile body -> ~/.config/zsh/local/login.local.zsh"
+    ' "${TARGET_HOME}/.zprofile" >"$zprofile_extract"
+    if file_has_content "$zprofile_extract"; then
+      cp "$zprofile_extract" "$LOCAL_ZSH"
+      echo "Migrated ~/.zprofile body -> ~/.config/zsh/local.zsh"
     fi
+    rm -f "$zprofile_extract"
   fi
 fi
 
+# Remove a broken local.zsh produced by an earlier stub-body migration.
+if [[ -f "$LOCAL_ZSH" ]] && grep -Fq 'local/login.local.zsh' "$LOCAL_ZSH" && ! grep -Eq 'cargo|OrbStack|MacPorts|Kiro|fnm' "$LOCAL_ZSH"; then
+  backup_file "$LOCAL_ZSH"
+  rm -f "$LOCAL_ZSH"
+  echo "Removed broken stub residue from local.zsh"
+fi
+
 backup_file "${TARGET_HOME}/.zshenv"
 backup_file "${TARGET_HOME}/.zshrc"
 backup_file "${TARGET_HOME}/.zprofile"
@@ -102,25 +137,19 @@ install -m 644 "${ROOT}/.zshenv" "${TARGET_HOME}/.zshenv"
 install -m 644 "${ROOT}/.zshrc" "${TARGET_HOME}/.zshrc"
 install -m 644 "${ROOT}/.zprofile" "${TARGET_HOME}/.zprofile"
 
-# Replace managed modules only (never touch local/).
+# Replace managed modules only (never touch local.zsh).
 rm -f "${ZSH_CFG}/env"/*.zsh
 rm -f "${ZSH_CFG}/interactive"/*.zsh
 rm -f "${ZSH_CFG}/login"/*.zsh
 install -m 644 "${ROOT}/config/env/"*.zsh "${ZSH_CFG}/env/"
 install -m 644 "${ROOT}/config/interactive/"*.zsh "${ZSH_CFG}/interactive/"
-# login may be empty of modules
 if compgen -G "${ROOT}/config/login/"*.zsh > /dev/null; then
   install -m 644 "${ROOT}/config/login/"*.zsh "${ZSH_CFG}/login/"
 fi
 
-# Seed examples only when missing (never overwrite user locals).
-for example in env.local.zsh login.local.zsh interactive.local.zsh; do
-  src="${ROOT}/local/${example}.example"
-  dst="${ZSH_CFG}/local/${example}.example"
-  if [[ -f "$src" ]]; then
-    install -m 644 "$src" "$dst"
-  fi
-done
+if [[ -f "${ROOT}/local.zsh.example" ]]; then
+  install -m 644 "${ROOT}/local.zsh.example" "${ZSH_CFG}/local.zsh.example"
+fi
 
 # Ensure intentional grok shim when the binary tree exists.
 if [[ -e "${TARGET_HOME}/.grok/bin/grok" ]]; then