Add jupytext to requirements and export Module 14

Requirements.txt updates:
- Added jupytext>=1.16.0 (required for tito export)
- Added nbformat>=5.10.0 (jupytext dependency)
- New section: Development Tools (Required for tito export)

Module 14 export:
- Successfully exported kvcaching_dev.py to tinytorch/generation/kv_cache.py
- Generated kvcaching_dev.ipynb (21 cells: 9 code, 12 markdown)
- KVCache class, enable_kv_cache(), disable_kv_cache() now in package

Auto-generated updates:
- Added DO NOT EDIT warnings to 8 exported files
- Updated _modidx.py with Module 14 exports
- Protected core files from manual editing

Export now works with: tito export 14_kvcaching
Students can import: from tinytorch.generation.kv_cache import enable_kv_cache

tinytorch/models/transformer.py

@@ -1,5 +1,19 @@
-# AUTOGENERATED! DO NOT EDIT! File to edit: ../../modules/source/13_transformers/transformers_dev.ipynb.
-
+# ╔═══════════════════════════════════════════════════════════════════════════════╗
+# ║                        🚨 CRITICAL WARNING 🚨                                ║
+# ║                     AUTOGENERATED! DO NOT EDIT!                              ║
+# ║                                                                               ║
+# ║  This file is AUTOMATICALLY GENERATED from source modules.                   ║
+# ║  ANY CHANGES MADE HERE WILL BE LOST when modules are re-exported!            ║
+# ║                                                                               ║
+# ║  ✅ TO EDIT: modules/source/XX_transformer/transformer_dev.py       ║
+# ║  ✅ TO EXPORT: Run 'tito module complete <module_name>'                      ║
+# ║                                                                               ║
+# ║  🛡️ STUDENT PROTECTION: This file contains optimized implementations.        ║
+# ║     Editing it directly may break module functionality and training.         ║
+# ║                                                                               ║
+# ║  🎓 LEARNING TIP: Work in modules/source/ - that's where real development    ║
+# ║     happens! The tinytorch/ directory is just the compiled output.           ║
+# ╚═══════════════════════════════════════════════════════════════════════════════╝
 # %% auto 0
 __all__ = ['LayerNorm', 'MLP', 'TransformerBlock', 'GPT']