feat: Revise documentation and examples for version 2.0.0

- Update QUICKSTART.md and README.md to reflect the new package name `costkatana` and simplify installation instructions.
- Enhance usage examples to demonstrate the new zero-configuration API and common patterns for AI interactions.
- Remove outdated examples and consolidate advanced features into a more streamlined format.
- Update setup.py to reflect the new package name and version 2.0.0.
- Improve clarity and consistency across all documentation regarding API key management and usage.

Author: abdulgeek

CHANGELOG.md

@@ -0,0 +1,106 @@
+# Changelog
+
+All notable changes to Cost Katana Python SDK will be documented in this file.
+
+## [2.0.0] - 2025-01-XX
+
+### 🚀 Major Release: Complete Simplification
+
+Complete redesign to make using AI in Python as simple as possible.
+
+### ✨ New Features
+
+#### Ultra-Simple API
+
+**New `ai()` function** - The easiest way to use AI:
+```python
+import cost_katana as ck
+response = ck.ai('gpt-4', 'Hello')
+print(response.text)
+print(f"Cost: ${response.cost}")
+```
+
+**New `chat()` function** - Simple chat sessions:
+```python
+import cost_katana as ck
+session = ck.chat('gpt-4')
+session.send('Hello')
+session.send('How are you?')
+print(f"Total: ${session.total_cost}")
+```
+
+#### Auto-Configuration
+- Automatically detects API keys from environment
+- Works with `COST_KATANA_KEY` or provider keys directly
+- Zero setup if environment is configured
+- Smart error messages with actionable steps
+
+#### SimpleResponse Object
+- Clean, simple response object
+- Direct access to `text`, `cost`, `tokens`
+- Bonus fields: `cached`, `optimized`, `provider`
+
+### 💥 Breaking Changes
+
+None! The traditional API (`GenerativeModel`) still works for backward compatibility.
+
+**You can still use**:
+```python
+model = ck.GenerativeModel('gpt-4')
+response = model.generate_content('Hello')
+```
+
+**Or use the new simple API**:
+```python
+response = ck.ai('gpt-4', 'Hello')
+```
+
+### 📚 Documentation
+
+- **Completely rewritten README**: Focus on simplicity
+- **Updated QUICKSTART**: 3-step process
+- **New examples**: Real-world use cases with simple API
+- **Migration guides**: From OpenAI, Anthropic, Google SDKs
+
+### 🎯 Comparison
+
+#### Before (v1.x)
+```python
+import cost_katana as ck
+
+ck.configure(api_key='dak_...')
+model = ck.GenerativeModel('gpt-4')
+response = model.generate_content('Hello')
+print(response.text)
+```
+
+#### After (v2.0)
+```python
+import cost_katana as ck
+
+response = ck.ai('gpt-4', 'Hello')
+print(response.text)
+```
+
+### 📦 Examples
+
+New streamlined examples:
+- `simple_examples.py` - All basic patterns
+- `basic_usage.py` - Getting started
+- Updated all existing examples to show both APIs
+
+### 🐛 Bug Fixes
+
+- Improved error messages
+- Better environment variable detection
+- More robust provider inference
+
+---
+
+## [1.0.0] - 2024-XX-XX
+
+### Initial Release
+- Multi-provider support
+- Cost tracking
+- Unified API
+- Configuration management