Delete unused refcount / Resource scaffolding in src/Methcla/Audio/Resource.hpp

[kaoskorobase]

Motivation

src/Methcla/Audio/Resource.hpp declares a family of refcount + resource-map helpers that are not used anywhere in the codebase. They predate the current implementation; the engine grew past them without anything referencing them, and the file is now load-bearing only as a place that compiles.

Independent of any larger design work — the dead code can be removed on its own.

Dead declarations to remove

All within src/Methcla/Audio/Resource.hpp:

• Reference (refcounted base class). Not inherited by Node, Synth, Group, AudioBus, or anything else.
• Resource<Id> template (refcount + env + id). Zero call sites outside the header.
• ResourceMap<Id, T> (pointer map). Zero call sites — the engine uses plain std::vector<Node*> / std::vector<std::shared_ptr<AudioBus>> instead.
• ResourceRef<T> (alias for methcla_boost::intrusive_ptr<T>). Zero call sites.
• intrusive_ptr_add_ref / intrusive_ptr_release template helpers. Only meaningful with the deleted types.

Verified via:

grep -rn "class Resource<\|: Reference\b\|: Resource<\|ResourceMap\b\|ResourceRef\b" src/ include/ tests/ plugins/ examples/

Only matches are the declarations themselves.

Renames in include/methcla/engine.hpp

The actually-used class in the same conceptual area:

• ResourceIdAllocator<Id, T> → IdAllocator<Id, T>. Currently instantiated as NodeIdAllocator and AudioBusIdAllocator (public typedefs at include/methcla/engine.hpp:620-621); the typedef names are preserved, only the underlying template is renamed.

The rename is independent justification: the class is a general-purpose id allocator, not specific to any "resource" concept.

Files affected

• src/Methcla/Audio/Resource.hpp — remove dead declarations. If the file becomes empty, delete it (and its inclusions, if any).
• include/methcla/engine.hpp — rename ResourceIdAllocator → IdAllocator; preserve the NodeIdAllocator and AudioBusIdAllocator typedef names.

Scope

In scope: deletion + the one rename above.

Out of scope: the wider Resource system design in #147. That work depends on these names being freed up, but the cleanup stands on its own merits and can be merged independently.