change: Implement comprehensive error handling framework

[mathysgrapotte]

Is your change request related to a problem? Please describe.

• Generic exceptions without debugging context
• Late discovery of type/config mismatches
• Difficult debugging in distributed pipeline executions
• Inconsistent error reporting across components

Describe the solution you'd like

Implement a unified error handling framework that:

1. 🏗️ Structured Exception Hierarchy
   • Base StimulusError with context formatting
   • Component-specific exceptions (EncoderError, LoaderConfigError, etc)
2. 🔍 Validation Layers
   • Type/IO validation decorators
   • Config schema validation helpers
3. 📌 Context Propagation
   • Error context managers for file/resource operations
   • Component context auto-attachment
4. 📋 Config Validation
   • Early validation of pipeline configurations
   • Clear missing/invalid key reporting
5. 📚 Documentation
   • Updated issue templates for error reports
   • Error handling guidelines for contributors

Describe alternatives you've considered

Additional context