Implement Event Hook Dispatch Pipeline #348

Objective

Implement the event dispatch pipeline allowing plugins to subscribe to emulator events (CPU cycles, frame rendering, memory access traps, system reset).

Scope & Requirements

• Define PluginEventHooks_t containing optional function pointers:
  • on_cpu_cycle(uint64_t total_cycles)
  • on_frame_ready(const uint32_t* pixels, int width, int height, int pitch)
  • on_memory_read(uint16_t addr, uint8_t value)
  • on_memory_write(uint16_t addr, uint8_t value)
  • on_frontend_render(SDL_Renderer* renderer)
  • on_reset(bool cold_reset)
• Implement hook registration inside PluginManager_t.
• Maintain fast-path dispatch arrays per hook type.
• When no plugins subscribe to a hook type (such as memory read/write traps or cycle ticks), bypass dispatch completely without branching overhead in the critical CPU loop.
• Ensure hook callbacks preserve CPU state and handle re-entrant safety during reset.

Testing & Verification

• Register multiple mock plugin hooks and dispatch frame, cycle, memory, and reset events, verifying callbacks fire with correct arguments in registration order.
• Register sparse hook structures containing null pointers for unhandled events and verify dispatches safely skip unhandled hooks without crashing.
• Unregister hooks and verify subsequent event dispatches no longer invoke unregistered callbacks.
• Verify event dispatch when the hook list is completely empty is a fast no-op.
• Benchmark the CPU execution loop with zero registered cycle or memory hooks to confirm zero performance penalty.
• Verify reset callbacks execute cleanly during both warm and cold emulator reset sequences.
• Test re-entrancy safety when a hook callback invokes a core state inspection function.

Acceptance Criteria

• Subscribed plugins receive callbacks on frame generation, memory access, and reset events.
• Unregistering or shutting down a plugin removes it from active dispatch lists.
• Emulation execution speed remains unaffected when no plugins subscribe to cycle-level hooks.