Initial commit: LangChain evolution tutorial deck (132 slides)

- Cover, TOC, 5 dividers, 3 recap slides
- 5 sections (chains, langgraph, deepagents, openswe, ecosystem)
- design-system.js with theme tokens + 9 helper functions
- research/: timeline + sources + per-tech notes
- final-compile.js + merge.js for rebuild pipeline
- output/: langchain-evolution.pptx (2.3 MB) + langchain-evolution.pdf (1.1 MB) + 7 sample previews

slides/section1-chains/slide-19.js

@@ -0,0 +1,57 @@
+// Slide 19: Tools -- @tool decorator + bind_tools
+// Code slide: define tools and pass them to a model via bind_tools.
+
+const ds = require('./design-system');
+
+function createSlide(pres, theme) {
+  const slide = pres.addSlide();
+  ds.helpers.slideBase(slide, pres, theme);
+
+  ds.helpers.addHeader(slide, pres, theme, {
+    eyebrow: 'STAGE 1: CHAINS',
+    section: 'Tools',
+    title: '@tool -- любая функция становится инструментом',
+    sectionNumber: 1,
+  });
+
+  ds.helpers.addCodeBlock(slide, pres, theme, {
+    x: 0.5, y: 1.5, w: 9.0, h: 3.25,
+    language: 'python',
+    filePath: 'examples/tool_basic.py',
+    code: [
+      'from langchain.tools import tool',
+      'from langchain.chat_models import init_chat_model',
+      '',
+      '@tool',
+      'def get_weather(city: str) -> str:',
+      '    """Get the current weather for a given city."""',
+      '    return f"Sunny, 22C in {city}"',
+      '',
+      '@tool',
+      'def search_docs(query: str, top_k: int = 3) -> list[str]:',
+      '    """Search internal documentation. Returns top_k snippets."""',
+      '    return [f"doc about {query} #{i}" for i in range(top_k)]',
+      '',
+      '# bind_tools -- модель знает, какие функции можно вызвать',
+      'model = init_chat_model("openai:gpt-4.1-mini")',
+      'bound = model.bind_tools([get_weather, search_docs])',
+      '',
+      'result = bound.invoke("What is the weather in Paris?")',
+      'print(result.tool_calls)',
+      '# [{"name": "get_weather", "args": {"city": "Paris"}, "id": "..."}]',
+    ].join('\n'),
+  });
+
+  ds.helpers.addCallout(slide, pres, theme, {
+    x: 0.5, y: 4.85, w: 9.0, h: 0.3,
+    kind: 'success',
+    text: 'docstring инструмента = описание, которое видит модель. Названия параметров должны быть говорящими.',
+  });
+
+  ds.helpers.addSourceLine(slide, pres, theme, {
+    source: 'python.langchain.com/docs/how_to/tool_calling/',
+  });
+  ds.helpers.addPageNumber(slide, pres, theme, 19);
+}
+
+module.exports = { createSlide };