fix: Add complete LightGBM implementation (create_points, predict_score)

Critical fixes that were missing from squash merge:
- Implement create_points() with use_base_score parameter
- Implement predict_score() and predict_scores()
- Fix leaf ID mapping bug (extract actual ID from node_index)
- Add base score normalization for balanced tree contributions
- Update tests and examples with score visualization

This completes the 0.2.7rc1 release.

Author: xRiskLab

examples/catboost-getting-started.ipynb

@@ -9,9 +9,10 @@
    },
    "source": [
     "# <span style=\"font-family: Arial, sans-serif; color:#97f788\">xbooster</span>\n",
+    "\n",
     "## <span style=\"font-family: Arial, sans-serif; color:navyblue\">CatBoost - Getting started</span>\n",
     "\n",
-    "<span style=\"font-family: Arial, sans-serif; color:navyblue\">Repo: <a href=\"https://github.com/xRiskLab/xBooster\" title=\"GitHub link\">https://github.com/xRiskLab/xBooster</a></span>"
+    "<span style=\"font-family: Arial, sans-serif; color:navyblue\">Repo: <a href=\"https://github.com/xRiskLab/xBooster\" title=\"GitHub link\">https://github.com/xRiskLab/xBooster</a></span>\n"
    ]
   },
   {
@@ -674,7 +675,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "### Compare performance of scores"
+    "### Compare performance of scores\n"
    ]
   },
   {
@@ -741,7 +742,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "### Plot feature importance"
+    "### Plot feature importance\n"
    ]
   },
   {
@@ -777,7 +778,7 @@
  ],
  "metadata": {
   "kernelspec": {
-   "display_name": ".venv",
+   "display_name": ".venv (3.10.16)",
    "language": "python",
    "name": "python3"
   },