Fix Doxyfile paths for repo-root invocation; add phlex-namespace API docs (configuration, handle, concurrency)

Co-authored-by: greenc-FNAL <2372949+greenc-FNAL@users.noreply.github.com>

Author: Copilot

docs/Doxyfile

@@ -6,8 +6,9 @@ PROJECT_BRIEF     = "A framework for parallel, hierarchical, and layered executi
 QUIET             = YES
 
 # -- Input and output directories --------------------------------------------
-INPUT             = ../phlex ../form
-OUTPUT_DIRECTORY  = doxygen
+# Paths are relative to the repository root; invoke as: doxygen docs/Doxyfile
+INPUT             = phlex form
+OUTPUT_DIRECTORY  = docs/doxygen
 RECURSIVE         = YES
 
 # -- Output formats ----------------------------------------------------------

docs/source/api/concurrency.rst

@@ -0,0 +1,6 @@
+concurrency
+============
+
+.. doxygenstruct:: phlex::concurrency
+   :members:
+   :undoc-members:

docs/source/api/configuration.rst

@@ -0,0 +1,6 @@
+configuration
+==============
+
+.. doxygenclass:: phlex::configuration
+   :members:
+   :undoc-members:

docs/source/api/handle.rst

@@ -0,0 +1,6 @@
+handle
+=======
+
+.. doxygenclass:: phlex::handle
+   :members:
+   :undoc-members:

docs/source/index.rst

@@ -8,15 +8,28 @@ Welcome to Phlex's documentation!
 
 .. toctree::
    :maxdepth: 2
-   :caption: Contents:
+   :caption: Plugin entry points:
 
    api/module_graph_proxy
    api/source_graph_proxy
    api/graph_proxy
    api/framework_graph
    api/registrar
+
+.. toctree::
+   :maxdepth: 2
+   :caption: Algorithm nodes:
+
    api/declared_transform
    api/declared_fold
    api/declared_unfold
+
+.. toctree::
+   :maxdepth: 2
+   :caption: Data model:
+
+   api/configuration
+   api/handle
+   api/concurrency
    api/product_store
    api/products