remove unused pulse registry scaffolding

[sebastianorbell-qm]

Summary

This draft PR removes the pulse-registry scaffolding that is not currently used by the runtime pulse wiring flow.

Today, default pulses are materialized directly in macro_engine.wiring._ensure_default_pulses() from concrete channel instances. The extra pulse_registry.py / register_default_component_pulse_factories() layer was not the active path and added confusion around where pulse-default changes should actually be made.

What Changed

• removed quam_builder/architecture/quantum_dots/operations/pulse_registry.py
• removed register_default_component_pulse_factories() and related reset plumbing
• updated operations/__init__.py exports to match the simplified pulse surface
• kept component_pulse_catalog.py as helper pulse builders only
• kept _ensure_default_pulses() as the single default-pulse materialization path
• updated pulse helper tests and docs to match the simplified design

Why

The pulse code had two competing shapes:

• an apparent component-type pulse registry
• the actual runtime materialization path in _ensure_default_pulses()

In practice, the registry layer was placeholder-only, while the wiring layer did the real work. Removing the unused layer makes the code clearer and makes future pulse changes easier to place correctly.

Impact

• no intended runtime behavior change for the existing default pulse wiring path
• reduced pulse-layer API surface and testing/reset scaffolding
• makes it clearer that new default pulse logic should be added in the runtime wiring pass

Validation

Ran:

pytest tests/architecture/quantum_dots/operations/test_pulse_catalog.py tests/architecture/quantum_dots/operations/test_catalog_reset.py tests/builder/quantum_dots/test_pulse_wiring.py

All 18 tests passed.

Notes

This branch was preserved from an exploratory cleanup so the change can be discussed separately from the ongoing QDAC/baseband pulse work.