refactor(shell): simplify zsh profile startup

Summary:
- Move reusable PATH setup into a shared .pathrc and source it from zsh
  login and interactive startup.
- Keep .zshenv minimal, and guard p10k, Oh My Zsh, and terminal-only
  setup so non-terminal shells stay quiet.
- Preserve Emacs vterm p10k support while skipping prompt-heavy setup in
  eshell-style sessions.

Rationale:
- The local profile had startup-time side effects, duplicate PATH/plugin
  setup, and non-terminal noise similar to the cleanup already done on
  dabel.
- Neutral helper names avoid personal prefixes in reusable profile code.

Tests:
- zsh -n ~/.zshenv ~/.zprofile ~/.zshrc ~/.pathrc
- zsh -lic 'print ok'
- INSIDE_EMACS=eshell TERM=dumb zsh -ic 'print ok; print theme=$ZSH_THEME'
- INSIDE_EMACS=vterm TERM=xterm-256color zsh -ic 'print ok; print theme=$ZSH_THEME'
- SSH_AUTH_SOCK=/tmp/test-sock zsh -lc 'printf "%s\n" "$SSH_AUTH_SOCK"'

Co-authored-by: Codex <codex@openai.com>

.pathrc

@@ -0,0 +1,101 @@
+# Shared PATH setup for local shells.
+# Source this from login and interactive startup files; it is idempotent.
+
+_pathrc_path_has() {
+    case ":${PATH:-}:" in
+        *:"$1":*) return 0 ;;
+        *) return 1 ;;
+    esac
+}
+
+_pathrc_path_remove() {
+    [ -n "${PATH:-}" ] || return 0
+
+    _pathrc_old_ifs=$IFS
+    IFS=:
+    _pathrc_new_path=
+    for _pathrc_dir in $PATH; do
+        [ "$_pathrc_dir" = "$1" ] && continue
+        [ -n "$_pathrc_dir" ] || continue
+        case ":$_pathrc_new_path:" in
+            *:"$_pathrc_dir":*) ;;
+            *)
+                if [ -n "$_pathrc_new_path" ]; then
+                    _pathrc_new_path="$_pathrc_new_path:$_pathrc_dir"
+                else
+                    _pathrc_new_path="$_pathrc_dir"
+                fi
+                ;;
+        esac
+    done
+    IFS=$_pathrc_old_ifs
+    PATH=$_pathrc_new_path
+}
+
+_pathrc_path_prepend() {
+    [ -d "$1" ] || return 0
+    _pathrc_path_remove "$1"
+
+    if [ -n "${PATH:-}" ]; then
+        PATH="$1:$PATH"
+    else
+        PATH="$1"
+    fi
+}
+
+_pathrc_path_append() {
+    [ -d "$1" ] || return 0
+    _pathrc_path_has "$1" && return 0
+
+    if [ -n "${PATH:-}" ]; then
+        PATH="$PATH:$1"
+    else
+        PATH="$1"
+    fi
+}
+
+if [ -d /opt/homebrew ]; then
+    export HOMEBREW_PREFIX=/opt/homebrew
+    export HOMEBREW_CELLAR=/opt/homebrew/Cellar
+    export HOMEBREW_REPOSITORY=/opt/homebrew
+fi
+
+export GEM_HOME="$HOME/.gem"
+export NVM_DIR="$HOME/.nvm"
+export ASDF_DATA_DIR="${ASDF_DATA_DIR:-$HOME/.asdf}"
+
+# Prepend in reverse priority order.
+_pathrc_path_prepend "$HOME/Documents/codex-tools/mcpgw-cli"
+_pathrc_path_prepend "$HOME/.fzf/bin"
+_pathrc_path_prepend "$HOME/.rd/bin"
+_pathrc_path_prepend "$HOME/work/flutter/bin"
+_pathrc_path_prepend "$HOME/bin"
+_pathrc_path_prepend "$HOME/.local/bin"
+_pathrc_path_prepend /usr/local/bin
+_pathrc_path_prepend "$ASDF_DATA_DIR/shims"
+_pathrc_path_prepend /opt/homebrew/sbin
+_pathrc_path_prepend /opt/homebrew/bin
+_pathrc_path_prepend /opt/homebrew/opt/ruby/bin
+_pathrc_path_prepend "$HOME/.gem/ruby/3.3.0/bin"
+_pathrc_path_prepend "$GEM_HOME/bin"
+
+_pathrc_path_append /usr/bin
+_pathrc_path_append /bin
+_pathrc_path_append /usr/sbin
+_pathrc_path_append /sbin
+
+if [ -n "${ZSH_VERSION:-}" ] && [ -d /opt/homebrew/share/zsh/site-functions ]; then
+    fpath=(/opt/homebrew/share/zsh/site-functions ${fpath:#/opt/homebrew/share/zsh/site-functions})
+fi
+
+if [ -d /opt/homebrew/share/info ]; then
+    case ":${INFOPATH:-}:" in
+        *:/opt/homebrew/share/info:*) ;;
+        *) export INFOPATH="/opt/homebrew/share/info:${INFOPATH:-}" ;;
+    esac
+fi
+
+export PATH
+
+unset -f _pathrc_path_has _pathrc_path_remove _pathrc_path_prepend _pathrc_path_append 2>/dev/null || true
+unset _pathrc_old_ifs _pathrc_new_path _pathrc_dir