Add modular dev environment installer, dotfiles, and desnap script

Adds a TUI-driven, rollback-capable installer (install/install.sh +
install/modules/*.sh) covering JS/Python/systems toolchains, dev tooling,
browsers, chat apps, GNOME extras, and misc setup (wakatime key, ssh/gpg
perms, apt mirror benchmarking), all sourced from each vendor's official
install method. bootstrap.sh stows the zsh/git/tmux/vscode dotfiles and
runs the installer; desnap.sh purges snapd and replaces default snaps with
apt/Flatpak equivalents.

install/modules/vscode.sh

@@ -0,0 +1,54 @@
+install_vscode() {
+  if has_cmd code; then
+    ok "vscode already installed"
+  else
+    apt_add_repo vscode /etc/apt/keyrings/packages.microsoft.gpg \
+      https://packages.microsoft.com/keys/microsoft.asc \
+      "deb [arch=$(deb_arch) signed-by=/etc/apt/keyrings/packages.microsoft.gpg] https://packages.microsoft.com/repos/code stable main"
+    apt_install code
+  fi
+
+  _vscode_install_extensions code
+  _vscode_mirror_cursor
+}
+
+# Installs every extension id listed in vscode/extensions.txt (exported from
+# this machine with `code --list-extensions`) into whichever editor binary
+# is passed — reused for both `code` and `cursor` since Cursor is a VS Code
+# fork that reads the same extension id format.
+_vscode_install_extensions() {
+  local bin="$1"
+  local list="${DOTFILES_DIR:?}/vscode/extensions.txt"
+  has_cmd "$bin" || return 0
+  [[ -f "$list" ]] || return 0
+
+  local installed
+  installed=$("$bin" --list-extensions 2>/dev/null || true)
+
+  local ext
+  while IFS= read -r ext; do
+    if [[ -z "$ext" || "$ext" == \#* ]]; then continue; fi
+    if grep -qxF "$ext" <<< "$installed"; then continue; fi
+    log "$bin: installing extension $ext"
+    "$bin" --install-extension "$ext" --force >/dev/null 2>&1 || warn "$bin: failed to install $ext"
+  done < "$list"
+  return 0
+}
+
+# Cursor reads ~/.config/Cursor/User/settings.json the same way VS Code
+# reads ~/.config/Code/User/settings.json. Symlinking it to the (stowed)
+# Code settings keeps both in sync from one source of truth in this repo.
+_vscode_mirror_cursor() {
+  local src="$HOME/.config/Code/User/settings.json"
+  local dest_dir="$HOME/.config/Cursor/User"
+  [[ -f "$src" ]] || return 0
+
+  mkdir -p "$dest_dir"
+  if [[ ! -e "$dest_dir/settings.json" ]]; then
+    ln -sf "$src" "$dest_dir/settings.json"
+    ok "mirrored VS Code settings to Cursor"
+  fi
+
+  if has_cmd cursor; then _vscode_install_extensions cursor; fi
+  return 0
+}