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-07.js

@@ -0,0 +1,54 @@
+// Slide 07: Streaming -- .stream() yields chunks progressively
+// Code slide: how to consume the model output as a stream.
+
+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: 'Streaming',
+    title: 'Потоковый вывод -- token за токеном',
+    sectionNumber: 1,
+  });
+
+  ds.helpers.addCodeBlock(slide, pres, theme, {
+    x: 0.5, y: 1.5, w: 9.0, h: 3.25,
+    language: 'python',
+    filePath: 'examples/streaming.py',
+    code: [
+      'from langchain.chat_models import init_chat_model',
+      '',
+      'model = init_chat_model("openai:gpt-4.1-mini")',
+      '',
+      '# .stream() -> итератор по AIMessageChunk',
+      'for chunk in model.stream("Write a haiku about Python"):',
+      '    # У каждого chunk-а есть .content (текст) и .response_metadata',
+      '    print(chunk.content, end="", flush=True)',
+      '',
+      'print()  # перевод строки после потока',
+      '',
+      '# Async-вариант: model.astream() -- то же самое в async-контексте',
+      'import asyncio',
+      '',
+      'async def main():',
+      '    async for chunk in model.astream("Write a haiku about async"):',
+      '        print(chunk.content, end="", flush=True)',
+    ].join('\n'),
+  });
+
+  ds.helpers.addCallout(slide, pres, theme, {
+    x: 0.5, y: 4.85, w: 9.0, h: 0.3,
+    kind: 'success',
+    text: 'AIMessageChunk можно складывать через оператор + -- для буферизации и метрик.',
+  });
+
+  ds.helpers.addSourceLine(slide, pres, theme, {
+    source: 'python.langchain.com/docs/how_to/streaming/',
+  });
+  ds.helpers.addPageNumber(slide, pres, theme, 7);
+}
+
+module.exports = { createSlide };