[C] Add support for forward hooks

[michalharakal]

Task description: Forward hooks and tape recorder implementation

• Introduced a lightweight forward-hooks mechanism to record module forward passes without affecting normal execution when disabled.

• Added ForwardHooks interface with two callbacks: onForwardBegin(module, input) and onForwardEnd(module, input, output).

• Extended the ExecutionContext with an optional hooks property (null means disabled), keeping zero cost for code paths when no hooks are provided.

• Plumbed hooks through concrete contexts:

  • DirectCpuExecutionContext and DefaultDataExecutionContext accept and expose _hooks so callers can enable recording per run.

• Implemented a simple TapeRecorder that collects entries (module id/name, input/output tensor specs: shape and dtype, and room for parameter refs) for each forward invocation.

• Added a small utility wrapper withForwardHooks(ctx, module, input) { … } and used it to instrument forwards with minimal intrusion:

  • Integrated in DualModule composition helpers so composed graphs are recorded as they execute.
  • Integrated in Embedding.forward, ensuring index-based layers are recorded too.

• Kept traversal compatibility by relying on ModuleNode for id/name/children/params, so the tape can be correlated with the model structure.

• Wrote a test ForwardHooksTapeTest that:

  • Creates a TapeRecorder and injects it into DirectCpuExecutionContext.
  • Runs Embedding.forward on a small input and asserts exactly one module invocation was recorded with the expected module name and output shape in the tape.

• Result: Developers can optionally attach a recorder for diagnostics, profiling, or future autodiff, with zero overhead when hooks are not supplied.