fix(scripts): handle missing uv gracefully with clear error and auto-install

Add shared ensure_uv() to common.sh that shows install instructions and
offers interactive auto-install via install_uv.sh. Remove the no-op
override in install_python.sh so the shared function takes effect.
Fix SC1091 shellcheck warnings with source directives.

Closes #24

Author: CybotTM

scripts/install_python.sh

@@ -2,13 +2,13 @@
 set -euo pipefail
 
 DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+# shellcheck source=scripts/lib/common.sh
 . "$DIR/lib/common.sh"
+# shellcheck source=scripts/lib/install_strategy.sh
 . "$DIR/lib/install_strategy.sh"
 
 ACTION="${1:-install}"
 
-ensure_uv() { :; }
-
 ensure_python_distro() {
   if ! have python3 && have apt-get; then sudo apt-get update && sudo apt-get install -y python3 python3-pip; fi
 }

scripts/lib/common.sh

@@ -39,7 +39,7 @@ pipx_uninstall() { have pipx && pipx uninstall "$1" || true; }
 
 # nvm helpers
 ensure_nvm_loaded() {
-  # shellcheck disable=SC1090
+  # shellcheck disable=SC1090,SC1091
   [ -s "$HOME/.nvm/nvm.sh" ] && . "$HOME/.nvm/nvm.sh" || true
 }
 
@@ -82,6 +82,28 @@ prefers_rbenv_ruby() {
   is_path_under "$p" "$HOME/.rbenv" || return 1
 }
 
+# Ensure uv is available, offer to install if missing
+ensure_uv() {
+  have uv && return 0
+  log "Error: uv is required but not installed."
+  log ""
+  log "Install uv:"
+  log "  curl -LsSf https://astral.sh/uv/install.sh | sh"
+  log ""
+  log "Or run: make upgrade-uv"
+  log ""
+  log "See: https://docs.astral.sh/uv/"
+  # Auto-install if interactive and install script exists
+  local install_script="${DIR:-}/install_uv.sh"
+  if [ -t 0 ] && [ -f "$install_script" ]; then
+    read -rp "Install uv now? [Y/n] " answer
+    case "${answer:-y}" in
+      [Yy]*|"") bash "$install_script" && have uv && return 0 ;;
+    esac
+  fi
+  return 1
+}
+
 # WSL detection
 is_wsl() {
   grep -qi microsoft /proc/version 2>/dev/null