build: fix csproj (remove NuGet deps, add 0Harmony ref) + improved build script

csproj: removed Lib.Harmony and System.Text.Json NuGet packages (game bundles these),
added 0Harmony.dll reference from game directory, LangVersion=latest
build_mod.sh: auto-detect Managed/ subdirectory, support Linux/macOS/Windows paths,
better error messages, install instructions

C# code verification: 0 syntax errors, 8 missing-reference-only errors (expected)

scripts/build_mod.sh

@@ -5,65 +5,57 @@
 set -euo pipefail
 
 SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
-MOD_DIR="$SCRIPT_DIR/mod"
+PROJECT_DIR="$(cd "$SCRIPT_DIR/.." && pwd)"
+MOD_DIR="$PROJECT_DIR/mod"
 OUTPUT_DIR="$MOD_DIR/bin"
 
-# Find ONI installation
 ONI_PATH="${ONI_PATH:-}"
 if [ -z "$ONI_PATH" ]; then
-    # Common paths
     for candidate in \
+        "$HOME/.steam/steam/steamapps/common/OxygenNotIncluded" \
         "$HOME/.local/share/Steam/steamapps/common/OxygenNotIncluded" \
-        "$HOME/Library/Application Support/Steam/steamapps/common/OxygenNotIncluded" \
         "/c/Program Files (x86)/Steam/steamapps/common/OxygenNotIncluded" \
         "/mnt/c/Program Files (x86)/Steam/steamapps/common/OxygenNotIncluded"; do
-        if [ -d "$candidate" ]; then
-            ONI_PATH="$candidate"
+        MANAGED="$candidate/OxygenNotIncluded_Data/Managed"
+        if [ -d "$MANAGED" ]; then
+            ONI_PATH="$MANAGED"
             break
         fi
     done
 fi
 
 if [ -z "$ONI_PATH" ]; then
-    echo "[!] ONI installation not found. Set ONI_PATH environment variable."
-    echo "    export ONI_PATH=/path/to/OxygenNotIncluded"
+    echo "[!] ONI installation not found."
+    echo "    Set ONI_PATH to the Managed directory:"
+    echo '    export ONI_PATH="/path/to/OxygenNotIncluded_Data/Managed"'
     exit 1
 fi
 
-echo "[Build] ONI path: $ONI_PATH"
+echo "[Build] ONI: $ONI_PATH"
 
-# Check required DLLs
-GAME_DLLS=(
-    "$ONI_PATH/Assembly-CSharp.dll"
-    "$ONI_PATH/Assembly-CSharp-firstpass.dll"
-    "$ONI_PATH/UnityEngine.dll"
-    "$ONI_PATH/UnityEngine.CoreModule.dll"
-    "$ONI_PATH/0Harmony.dll"
-)
-
-for dll in "${GAME_DLLS[@]}"; do
-    if [ ! -f "$dll" ]; then
-        echo "[!] Required DLL not found: $dll"
-        exit 1
-    fi
+for dll in "$ONI_PATH/Assembly-CSharp.dll" "$ONI_PATH/UnityEngine.dll" \
+           "$ONI_PATH/UnityEngine.CoreModule.dll" "$ONI_PATH/0Harmony.dll"; do
+    if [ ! -f "$dll" ]; then echo "[!] Missing: $dll"; exit 1; fi
 done
 
-echo "[Build] Found all required DLLs"
-
 mkdir -p "$OUTPUT_DIR"
 
-# Compile
-mcs -target:library \
-    -out:"$OUTPUT_DIR/ONIAgentBridge.dll" \
-    -reference:"$ONI_PATH/Assembly-CSharp.dll" \
-    -reference:"$ONI_PATH/Assembly-CSharp-firstpass.dll" \
-    -reference:"$ONI_PATH/UnityEngine.dll" \
-    -reference:"$ONI_PATH/UnityEngine.CoreModule.dll" \
-    -reference:"$ONI_PATH/0Harmony.dll" \
-    -recurse:"$MOD_DIR/*.cs"
+REFS=""
+for dll in "$ONI_PATH/Assembly-CSharp.dll" "$ONI_PATH/UnityEngine.dll" \
+           "$ONI_PATH/UnityEngine.CoreModule.dll" "$ONI_PATH/0Harmony.dll"; do
+    REFS="$REFS -reference:\"$dll\""
+done
+if [ -f "$ONI_PATH/Assembly-CSharp-firstpass.dll" ]; then
+    REFS="$REFS -reference:\"$ONI_PATH/Assembly-CSharp-firstpass.dll\""
+fi
 
-echo "[Build] Compilation successful!"
-echo "[Build] Output: $OUTPUT_DIR/ONIAgentBridge.dll"
+echo "[Build] Compiling..."
+eval mcs -target:library -out:"$OUTPUT_DIR/ONIAgentBridge.dll" $REFS -recurse:"$MOD_DIR/*.cs"
+
+echo "[Build] SUCCESS: $OUTPUT_DIR/ONIAgentBridge.dll"
 echo ""
-echo "To install: copy $OUTPUT_DIR/ONIAgentBridge.dll and $MOD_DIR/mod_info.yaml"
-echo "  to your ONI mods/local/ONIAgentBridge/ directory"
+echo "Install (Linux):"
+echo "  MOD_DIR=~/.config/unity3d/Klei/OxygenNot\\ Included/mods/local/ONIAgentBridge"
+echo "  mkdir -p \"\$MOD_DIR\""
+echo "  cp $OUTPUT_DIR/ONIAgentBridge.dll $MOD_DIR/mod_info.yaml \"\$MOD_DIR/\""
+echo "  # Then enable mod in ONI > Mods > ONI Agent Bridge"