Add seasonal palettes and selection prompts

- Implement dynamic/static season support in shared PS1

- Add season selection prompts to Linux and macOS installers

dotfiles/install/install-linux-global.sh

@@ -23,6 +23,8 @@ MARKER_END="# <<< dotfiles (managed) <<<"
 # Select install mode (PS1, banner, or both)
 install_ps1=1
 install_banner=1
+season_mode="dynamic"
+season_choice=""
 if [[ -t 0 ]]; then
   echo "Install options:"
   echo "  1) PS1 only"
@@ -35,6 +37,39 @@ if [[ -t 0 ]]; then
     ""|3) install_ps1=1; install_banner=1 ;;
     *) echo "Invalid choice, using both."; install_ps1=1; install_banner=1 ;;
   esac
+
+  if [[ "$install_ps1" -eq 1 ]]; then
+    echo
+    echo "Season mode:"
+    echo "  1) Dynamic (auto by date)"
+    echo "  2) Static (pick one season)"
+    read -r -p "Choose [1]: " season_mode_choice
+    case "${season_mode_choice}" in
+      2)
+        season_mode="static"
+        echo "Pick a season:"
+        echo "  1) Winter"
+        echo "  2) Spring"
+        echo "  3) Summer"
+        echo "  4) Autumn"
+        read -r -p "Choose [1]: " season_pick
+        case "${season_pick}" in
+          2) season_choice="spring" ;;
+          3) season_choice="summer" ;;
+          4) season_choice="autumn" ;;
+          ""|1) season_choice="winter" ;;
+          *) echo "Invalid choice, using winter."; season_choice="winter" ;;
+        esac
+        ;;
+      ""|1)
+        season_mode="dynamic"
+        ;;
+      *)
+        echo "Invalid choice, using dynamic."
+        season_mode="dynamic"
+        ;;
+    esac
+  fi
 fi
 
 if [[ "$install_banner" -eq 1 ]]; then
@@ -94,8 +129,17 @@ fi
 if [[ "$install_ps1" -eq 1 ]]; then
   cp -f "$SRC_PS1" "$DST_PS1"
   chmod 0644 "$DST_PS1"
+
+  {
+    printf 'PS1_SEASON_MODE=%s\n' "$season_mode"
+    if [[ "$season_mode" == "static" && -n "$season_choice" ]]; then
+      printf 'PS1_SEASON=%s\n' "$season_choice"
+    fi
+  } > /etc/ps1-season
+  chmod 0644 /etc/ps1-season
 else
   rm -f "$DST_PS1"
+  rm -f /etc/ps1-season
 fi
 
 if [[ "$install_banner" -eq 1 ]]; then