📦 NEW: Advance Examples

[arre-ankit]

TLDR

• Added advanced pipe and agent examples demonstrating structured outputs and advanced chat functionality.
• Refactored codebase to replace "lb" references with "langbase" for consistency.

Dive Deeper

This PR introduces a comprehensive set of pipe examples that covers:

• pipe.run.stream.llmkey.py - Streaming with custom LLM API keys for cost management
• pipe.run.stream.chat.py - Multi-turn streaming conversations with thread continuity
• pipe.structured.outputs.py - Structured JSON outputs with Pydantic model validation and schema generation
• pipe.run.chat.py - Non-streaming conversation continuity with thread management
• pipe.run.pipe.key.py - Using pipe-specific API keys for granular access control