Create obd_ai foundation: session manager and approved command catalog

[virtuscyber]

Summary

Create the foundational obd_ai package that wraps the existing low-level python-OBD library with a higher-level session abstraction and an approved command catalog for LLM-safe access.

Why

The current repository exposes low-level OBD command primitives directly. For LLM integration we need a constrained, explicit, testable layer that models safe diagnostic capabilities without exposing arbitrary raw command access.

Scope

• Add an obd_ai/ package (or equivalent namespace) for higher-level integration code
• Implement a session manager around obd.OBD and optionally obd.Async
• Create an approved command catalog with metadata such as:
  • public tool name
  • backing obd.commands.* command
  • category
  • read/write classification
  • expected response type
  • human description
• Exclude arbitrary raw hex command construction from the high-level layer
• Add focused unit tests for catalog integrity and basic session lifecycle behavior

Acceptance Criteria

• obd_ai package exists with a clear boundary from core library code
• Approved command catalog covers the MVP read-only diagnostics set
• Session manager can connect, report status, and expose a controlled command lookup path
• No high-level API surface allows arbitrary custom command execution in MVP
• Tests verify catalog contents and session wiring behavior