docs(notebook): restore Core principles block in usage guide

Keep author-facing intro markdown with ARS and Ethnography citations.

Author: Corey-Abramson

visualization_toolkit_final.ipynb

@@ -18,11 +18,16 @@
     "\n",
     "**Key parameters (set per tool):** `clustering_method` 1 = RoBERTa, 2 = Jaccard, 3 = PMI, 4 = TF-IDF; `distance_metric` `\"cosine\"` or `\"default\"`. Design rationale for the environment-configuration and word-family setup steps is in [README → Design Notes](https://github.com/Computational-Ethnography-Lab/cmap_visualization_toolkit#design-notes).\n",
     "\n",
-    "## License & Citation\n",
+    "## Core principles \n",
+    "- Abramson, C. M., Prendergast, T., Li, Z., & Dohan, D. (2026). \"Qualitative Research in an Era of Artificial Intelligence: A Pragmatic Approach to Data Analysis, Workflow, and Computation.\" *Annual Review of Sociology, 52* (in press). https://doi.org/10.1146/annurev-soc-011824-104836\n",
+    "\n",
+    "- Abramson, C. M., Joslyn, J., Rendle, K. A., Garrett, S. B., & Dohan, D. (2018). The promises of computational ethnography: Improving transparency, replicability, and validity for realist approaches to ethnographic analysis. Ethnography, 19(2), 254-284.\n",
     "\n",
-    "BSD 3-Clause (\"AS IS\", no warranty). **Cite as:** Abramson, Corey M. and Yuhan (Victoria) Nian. 2025. *CMAP Visualization Toolkit.* Full citation with the Zenodo DOI and contributor list is in the [README](https://github.com/Computational-Ethnography-Lab/cmap_visualization_toolkit#policies). Questions: <corey.abramson@rice.edu>.\n",
+    "## License & Citation\n",
     "\n",
-    "**Acknowledgments:** Thanks to Alejandro for feedback and testing."
+    "BSD 3-Clause (\"AS IS\", no warranty). \n",
+    "**Cite as:** Abramson, Corey M. and Yuhan (Victoria) Nian. 2025. *CMAP Visualization Toolkit.* \n",
+    "Full citation with the Zenodo DOI and contributor list is in the [README](https://github.com/Computational-Ethnography-Lab/cmap_visualization_toolkit#policies). Questions: <corey.abramson@rice.edu>.\n"
    ]
   },
   {
@@ -40,13 +45,13 @@
    "execution_count": null,
    "id": "9217d283",
    "metadata": {
-    "tags": [
-     "setup-run-once"
-    ],
+    "collapsed": true,
     "jupyter": {
      "source_hidden": true
     },
-    "collapsed": true
+    "tags": [
+     "setup-run-once"
+    ]
    },
    "outputs": [],
    "source": [
@@ -514,11 +519,12 @@
   {
    "cell_type": "code",
    "execution_count": null,
+   "id": "fc1758ce",
    "metadata": {
+    "collapsed": true,
     "jupyter": {
      "source_hidden": true
-    },
-    "collapsed": true
+    }
    },
    "outputs": [],
    "source": [
@@ -2270,6 +2276,7 @@
   {
    "cell_type": "code",
    "execution_count": null,
+   "id": "563ad982",
    "metadata": {},
    "outputs": [],
    "source": [
@@ -2946,6 +2953,7 @@
   {
    "cell_type": "code",
    "execution_count": null,
+   "id": "f8a025f8",
    "metadata": {},
    "outputs": [],
    "source": [