Server launcher and start-up checks for other machines

- server/run_server.sh: checks Godot is 4.7+, imports a fresh copy once
  (the class cache in .godot/ isn't in git), then starts the server
- The dedicated server refuses to start, with a clear reason, on Godot
  older than 4.7 or when the game's scripts failed to load, instead of
  claiming to listen
- tests/run_all.sh imports a fresh copy first
- Setup doc: 4.7+ (not 4.3+), importing a fresh copy, running a server

docs/SETUP_ON_NEW_MACHINE.md

@@ -4,14 +4,39 @@ This project is a self-contained git repo. Everything needed to build and run is
 in it except **Godot itself** (which you install once per machine). No assets to
 download — the M0 world is generated in code.
 
-## 1. Install Godot 4.3+
+## 1. Install Godot 4.7+
 - **macOS / Windows / Linux:** download the *standard* build (NOT the .NET/C#
   build — this project is pure GDScript) from https://godotengine.org/download
-- Use **4.7.x or newer 4.x**. The project was upgraded to `4.7.2.stable` (an
+- Use **4.7.x or newer 4.x**. The project is on `4.7.2.stable`. **Older
-  older editor will warn that the project is from a newer version).
+  versions (4.3 etc.) can't run it**: they fail with script errors. Check
+  with `godot --version`, or `/Applications/Godot.app/Contents/MacOS/Godot
+  --version` on a Mac.
 - macOS shortcut: `brew install --cask godot`. If Homebrew can't unpack it,
   download the zip from the GitHub release page and move `Godot.app` to
-  `/Applications`.
+  `/Applications` (replacing any older one).
+
+## 2. First run on a fresh copy: import once
+Godot keeps its list of named classes (e.g. `Inventory`) in `.godot/`, which
+isn't in git. Opening the project in the editor creates it. If you only run
+**headless** (a server, or the tests), import once after cloning:
+```bash
+godot --headless --path . --import
+```
+Without it you get errors like `Could not find type "Inventory"`.
+`server/run_server.sh` and `tests/run_all.sh` do this for you.
+
+## 3. Running a dedicated server
+```bash
+server/run_server.sh                              # settings from server.json
+server/run_server.sh --server-name "Paul's island" --password secret --port 24242
+```
+It checks the Godot version, imports a fresh copy, then starts the server on
+UDP 24242 with no window. Settings live in `server.json` (its path is printed
+at start-up; on macOS it's under
+`~/Library/Application Support/Godot/app_userdata/Valheimlike/server/`).
+Stop it with Ctrl+C. Players join with **Join Game** on the title screen. Over
+Tailscale, use the server machine's 100.x address or its machine name. See
+`docs/MULTIPLAYER_PLAN.md` for all the options.
 
 ## Tests
 Run everything (fails on any failed check or script error):

scripts/net/net.gd

@@ -144,7 +144,26 @@ func is_server() -> bool:
 
 # --- server -------------------------------------------------------------------
 
+## Why this Godot can't run the server ("" = it can): too old, or the game's
+## scripts failed to load (usually a fresh copy that's never been imported).
+func startup_problem() -> String:
+	var v := Engine.get_version_info()
+	if v.major < 4 or (v.major == 4 and v.minor < 7):
+		return "This game needs Godot 4.7 or newer, but this is %s. Download 4.7.2 from https://godotengine.org/download" % v.string
+	var root: Window = (Engine.get_main_loop() as SceneTree).root
+	for n in ["ItemDB", "Actions", "Saves"]:
+		var node := root.get_node_or_null(n)
+		if node == null or node.get_script() == null:
+			return "The game's scripts didn't load (see the errors above). If this is a fresh copy of the project, " + \
+				"import it once first:  godot --headless --path . --import   (server/run_server.sh does this for you)"
+	return ""
+
 func _start_dedicated() -> void:
+	var bad := startup_problem()
+	if not bad.is_empty():
+		printerr("[server] Not starting: ", bad)
+		get_tree().quit(1)
+		return
 	var err := start_server(String(_args.get("config", ServerConfig.DEFAULT_PATH)), _args)
 	if not err.is_empty():
 		printerr("[server] ", err)

server/run_server.sh

@@ -0,0 +1,44 @@
+#!/bin/sh
+# Starts a dedicated Valheimlike server (no window, no local player).
+#
+#   server/run_server.sh                       defaults from server.json
+#   server/run_server.sh --port 24242 --server-name "Paul's island" --password secret
+#
+# Any flags are passed to the server (see docs/MULTIPLAYER_PLAN.md §2).
+# Set GODOT=/path/to/godot to use a particular Godot. Stop it with Ctrl+C.
+#
+# Before starting it checks that Godot is 4.7 or newer, and imports a fresh
+# copy of the project once (Godot's class cache lives in .godot/, which isn't
+# in git, so a new clone can't run headless until it has been imported).
+
+cd "$(dirname "$0")/.." || exit 1
+
+GODOT="${GODOT:-godot}"
+if ! command -v "$GODOT" >/dev/null 2>&1; then
+	# macOS: use the app bundle if `godot` isn't on the PATH.
+	if [ -x /Applications/Godot.app/Contents/MacOS/Godot ]; then
+		GODOT=/Applications/Godot.app/Contents/MacOS/Godot
+	else
+		echo "Can't find Godot. Install 4.7.2 from https://godotengine.org/download, or set GODOT=/path/to/godot" >&2
+		exit 1
+	fi
+fi
+
+version=$("$GODOT" --version 2>/dev/null | tail -n 1)
+major=$(echo "$version" | cut -d. -f1)
+minor=$(echo "$version" | cut -d. -f2)
+if [ -z "$major" ] || [ "$major" -lt 4 ] || { [ "$major" -eq 4 ] && [ "$minor" -lt 7 ]; }; then
+	echo "This game needs Godot 4.7 or newer, but $GODOT is ${version:-unknown}." >&2
+	echo "Download 4.7.2 from https://godotengine.org/download (or set GODOT=/path/to/a/newer/godot)" >&2
+	exit 1
+fi
+
+if [ ! -f .godot/global_script_class_cache.cfg ]; then
+	echo "First run on this copy: importing the project (a few seconds)..."
+	if ! "$GODOT" --headless --path . --import >/dev/null 2>&1 || [ ! -f .godot/global_script_class_cache.cfg ]; then
+		echo "Import failed. Try: $GODOT --headless --path . --import" >&2
+		exit 1
+	fi
+fi
+
+exec "$GODOT" --headless --path . -- --server "$@"

tests/run_all.sh

@@ -4,6 +4,11 @@
 # Usage: tests/run_all.sh   (from the repo root; needs `godot` on PATH)
 cd "$(dirname "$0")/.." || exit 1
 status=0
+# A fresh clone has no class cache yet (.godot/ isn't in git): import once.
+if [ ! -f .godot/global_script_class_cache.cfg ]; then
+	echo "Importing the project first (fresh copy)..."
+	godot --headless --path . --import >/dev/null 2>&1
+fi
 for t in test_survival_core test_survival_stats test_save_load test_weather_building test_creatures_combat test_wolves test_fishing_diet test_net_lobby test_net_world test_terrain_edges test_boundary; do
 	extra=""
 	[ "$t" = "test_boundary" ] && extra="--fixed-fps 30"