docs(docs): fix grammar, capitalization, and style issues across documentation (#32503)

**Changes made:**
- Fix 'Async programming with langchain' → 'Async programming with
LangChain'
- Fix 'Langchain asynchronous APIs' → 'LangChain asynchronous APIs'
- Fix 'How to: init any model' → 'How to: initialize any model'
- Fix 'async programming with Langchain' → 'async programming with
LangChain'
- Fix 'How to propagate callbacks constructor' → 'How to propagate
callbacks to the constructor'
- Fix 'How to add a semantic layer over graph database' → 'How to add a
semantic layer over a graph database'
- Fix 'Build a Question/Answering system' → 'Build a Question-Answering
system'

**Why is this change needed?**
- Improves documentation clarity and readability
- Maintains consistent LangChain branding throughout the docs
- Fixes grammar issues that could confuse users
- Follows proper documentation standards

**Files changed:**
- `docs/docs/concepts/async.mdx`
- `docs/docs/concepts/tools.mdx`
- `docs/docs/how_to/index.mdx`
- `docs/docs/how_to/callbacks_constructor.ipynb`
- `docs/docs/how_to/graph_semantic.ipynb`
- `docs/docs/tutorials/sql_qa.ipynb`

**Issue:** N/A (documentation improvements)

**Dependencies:** None

**Twitter handle:** https://x.com/mishraravibhush

Co-authored-by: Mason Daugherty <mason@langchain.dev>

docs/docs/concepts/async.mdx

@@ -1,4 +1,4 @@
-# Async programming with langchain
+# Async programming with LangChain
 
 :::info Prerequisites
 * [Runnable interface](/docs/concepts/runnables)
@@ -12,7 +12,7 @@ You are expected to be familiar with asynchronous programming in Python before r
 This guide specifically focuses on what you need to know to work with LangChain in an asynchronous context, assuming that you are already familiar with asynchronous programming.
 :::
 
-## Langchain asynchronous APIs
+## LangChain asynchronous APIs
 
 Many LangChain APIs are designed to be asynchronous, allowing you to build efficient and responsive applications.
 

docs/docs/concepts/tools.mdx

@@ -31,7 +31,7 @@ The key attributes that correspond to the tool's **schema**:
 The key methods to execute the function associated with the **tool**:
 
 - **invoke**: Invokes the tool with the given arguments.
-- **ainvoke**: Invokes the tool with the given arguments, asynchronously. Used for [async programming with Langchain](/docs/concepts/async).
+- **ainvoke**: Invokes the tool with the given arguments, asynchronously. Used for [async programming with LangChain](/docs/concepts/async).
 
 ## Create tools using the `@tool` decorator
 

docs/docs/how_to/index.mdx

@@ -34,7 +34,7 @@ These are the core building blocks you can use when building applications.
 [Chat Models](/docs/concepts/chat_models) are newer forms of language models that take messages in and output a message.
 See [supported integrations](/docs/integrations/chat/) for details on getting started with chat models from a specific provider.
 
-- [How to: init any model in one line](/docs/how_to/chat_models_universal_init/)
+- [How to: initialize any model in one line](/docs/how_to/chat_models_universal_init/)
 - [How to: work with local models](/docs/how_to/local_llms)
 - [How to: do function/tool calling](/docs/how_to/tool_calling)
 - [How to: get models to return structured output](/docs/how_to/structured_output)