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-16.js

@@ -0,0 +1,56 @@
+// Slide 16: RunnableLambda + RunnablePassthrough -- custom logic in pipeline
+// Code slide: insert arbitrary Python functions into an LCEL chain.
+
+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: 'Runnable helpers',
+    title: 'RunnableLambda + RunnablePassthrough',
+    sectionNumber: 1,
+  });
+
+  ds.helpers.addCodeBlock(slide, pres, theme, {
+    x: 0.5, y: 1.5, w: 9.0, h: 3.25,
+    language: 'python',
+    filePath: 'examples/runnable_lambda.py',
+    code: [
+      'from langchain_core.runnables import RunnableLambda, RunnablePassthrough',
+      '',
+      '# RunnableLambda -- оборачивает произвольную функцию',
+      'upper = RunnableLambda(lambda x: x.upper())',
+      'word_count = RunnableLambda(lambda text: {"text": text, "words": len(text.split())})',
+      '',
+      '# RunnablePassthrough -- пропускает вход дальше (для branching)',
+      'passthrough = RunnablePassthrough()',
+      '',
+      '# Пример: текст -> uppercase -> посчитать слова -> смёрджить с оригиналом',
+      'chain = (',
+      '    word_count',
+      '    | RunnablePassthrough.assign(upper=upper)',
+      ')',
+      '',
+      'result = chain.invoke("hello world from langchain")',
+      'print(result)',
+      '# {"text": "hello world from langchain",',
+      '#  "words": 4, "upper": "HELLO WORLD FROM LANGCHAIN"}',
+    ].join('\n'),
+  });
+
+  ds.helpers.addCallout(slide, pres, theme, {
+    x: 0.5, y: 4.85, w: 9.0, h: 0.3,
+    kind: 'info',
+    text: 'RunnablePassthrough.assign -- добавляет новые ключи, сохраняя исходные. Идеален для RAG-style цепочек.',
+  });
+
+  ds.helpers.addSourceLine(slide, pres, theme, {
+    source: 'python.langchain.com/docs/how_to/functions/',
+  });
+  ds.helpers.addPageNumber(slide, pres, theme, 16);
+}
+
+module.exports = { createSlide };