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-15.js

@@ -0,0 +1,58 @@
+// Slide 15: Async + configurable -- ainvoke/astream + chain.config
+// Code slide: how to use chains from async code and override params at call site.
+
+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',
+    title: 'async + config -- полный контроль',
+    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_async.py',
+    code: [
+      'import asyncio',
+      'from langchain_core.runnables import ConfigurableField',
+      '',
+      '# Любой Runnable имеет ainvoke / astream / abatch',
+      'async def main():',
+      '    # Один async-вызов',
+      '    result = await chain.ainvoke({"language": "French", "text": "Hi"})',
+      '',
+      '    # Async stream',
+      '    async for chunk in chain.astream({"language": "French", "text": "Hi"}):',
+      '        print(chunk, end="", flush=True)',
+      '',
+      'asyncio.run(main())',
+      '',
+      '# configurable_fields -- параметры, которые можно переопределять',
+      '# на лету через config={"configurable": {...}}',
+      'configurable_chain = init_chat_model("openai:gpt-4.1-mini",',
+      '    temperature=0.7).configurable_fields(',
+      '    temperature=ConfigurableField(id="temperature"),',
+      ')',
+      '# configurable_chain.invoke(messages, config={"configurable": {"temperature": 0.0}})',
+    ].join('\n'),
+  });
+
+  ds.helpers.addCallout(slide, pres, theme, {
+    x: 0.5, y: 4.85, w: 9.0, h: 0.3,
+    kind: 'success',
+    text: 'configurable_fields + config={"configurable": {...}} -- паттерн для multi-tenant LLM-приложений.',
+  });
+
+  ds.helpers.addSourceLine(slide, pres, theme, {
+    source: 'python.langchain.com/docs/how_to/configurable/',
+  });
+  ds.helpers.addPageNumber(slide, pres, theme, 15);
+}
+
+module.exports = { createSlide };