Define core domain models and interfaces (ExecutionStep, ExecutionTrace, BaseVisualizer)

[MaximilianRau04]

Context

The repository currently contains only a LICENSE file. Before any visualizer can be implemented, we need the shared vocabulary the rest of the engine will build on: how a captured execution is represented, and the contract every visualizer implements.

What

Define the core domain models and abstract interfaces:

• Models: ExecutionStep (line number, event type such as line/call/return, local variable snapshot, timestamp/step index), ExecutionTrace (ordered list of ExecutionStep, target function metadata), VisualizationFrame (the renderable state derived from one or more steps, e.g. current pointer positions, highlighted nodes).
• Interfaces: BaseTracer (produces an ExecutionTrace from a function + inputs), BaseVisualizer (consumes an ExecutionTrace and produces a sequence of VisualizationFrame), BaseRenderer (consumes VisualizationFrames and produces output, e.g. terminal text or HTML).

This mirrors the interface/model split already established in the dsa-autopsy and complexity-lab sibling projects and should unblock the tracer and visualizer implementations.

Acceptance Criteria

• Dataclasses for ExecutionStep, ExecutionTrace, VisualizationFrame added under models/
• BaseTracer, BaseVisualizer, BaseRenderer ABCs added under interfaces/ with documented abstract methods
• Unit tests covering model construction/equality
• mypy/ruff clean