claw: Linux kernel-style OOP refactoring

[zevorn]

Goal

Apply Linux kernel OOP design patterns to refactor all major RT-Claw subsystems, following the methodology from LWN Articles 444910 and 446317.

Design Patterns

• Struct embedding + container_of for data inheritance (replacing all void* opaque handles)
• Function pointer tables (ops structs) for polymorphism and method dispatch
• Linker section auto-registration for zero-cost component discovery (GNU ld) / __attribute__((constructor)) (ESP-IDF)
• Unified error codes (claw_err_t) and base class definitions as shared infrastructure

Scope

• OSAL layer: struct-based types replacing void*
• Gateway: polymorphic message dispatch via ops vtable
• Services: private context structs with lifecycle state machine and dependency graph
• Drivers: probe/remove lifecycle with struct claw_driver base
• Tools: struct claw_tool base class with ops vtable
• Scheduler: intrusive linked list replacing static array
• All 5 platforms: ESP32-C3, ESP32-S3, vexpress-a9, zynq-a9, Linux

Reference

• Plan: .humanize/plans/oop-refactor-plan.md
• LWN Article 1: https://lwn.net/Articles/444910/
• LWN Article 2: https://lwn.net/Articles/446317/

[zevorn]

#95