Dependency identity and invalidation
====================================

``DependencyGraph`` is a persistent directed acyclic graph used to answer two
separate questions: **is this product the same?** and **what work must run?** A
32-byte content digest answers the first; node-kind dirty flags answer the second.
Calling it a Merkle DAG is not enough because a source edit is not automatically
the identity parent of every semantic compiler result.

::

   scene.slang -> imported project.noise -> reflected entry point -> pipeline
                                           |                     ^
                                           `-> parameter layout -+
                                                +-> UI schema
                                                `-> parameter values

Source and imported-module nodes identify authored inputs. Compilation yields
independently hashed entry-point, UI-schema, parameter-layout, resource, and
pipeline products. Stable dependency keys are canonicalized, so order does not
accidentally change identity and shared modules need not be copied into a tree.

Why separation matters
----------------------

Changing ``UIName`` can change the inspector schema without changing uniform byte
layout, so it should not rebuild a GPU pipeline. A slider changes parameter values
and normally requests only a uniform upload. An imported module edit invalidates
documents that resolved that module. A binding-layout change requests binding and
pipeline work even if a label did not change.

The Inspector presents authored sources/imports first and keeps internal compiler
and renderer products under an advanced branch.

Implementation
--------------

``NodeId`` identifies a stable graph node; ``NodeKind`` selects invalidation semantics.
Relevant source is ``cpp/include/miskeyed/workbench/core/DependencyGraph.h``, its
implementation, and graph construction in ``cpp/src/workbench/slang/ShaderDocument.cpp``.