docs: fix strict-build cross-refs to private _descriptor_spec

The setting/attach_option consolidation added mkdocstrings autoref links
([`_SpecBase`][vgi.catalog._descriptor_spec._SpecBase] etc.) pointing at the
private _descriptor_spec module, which is not rendered in the API docs — so
`mkdocs build --strict` aborted on unresolved cross-reference targets.
Demote those links to plain code spans naming the module.

Verified: `mkdocs build --strict` exits 0 with no autoref warnings.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: rustyconover

vgi/catalog/attach_option.py

@@ -27,7 +27,7 @@ class AttachOptionSpec(_SpecBase):
     """Extracted attach-option metadata for catalog discovery serialization.
 
     The resolved form of an `AttachOption`. See
-    [`_SpecBase`][vgi.catalog._descriptor_spec._SpecBase] for the field and
+    `_SpecBase` (in `vgi.catalog._descriptor_spec`) for the field and
     wire-format definition.
     """
 
@@ -39,7 +39,7 @@ class AttachOption(_DescriptorBase):
     Use with Annotated type hints to declare options in a Worker's
     AttachOptions inner class. The Arrow type is resolved from the base type
     in the Annotated hint. See
-    [`_DescriptorBase`][vgi.catalog._descriptor_spec._DescriptorBase] for the
+    `_DescriptorBase` (in `vgi.catalog._descriptor_spec`) for the
     ``desc`` and ``arrow_type`` attributes.
     """
 

vgi/catalog/setting.py

@@ -23,7 +23,7 @@ class SettingSpec(_SpecBase):
     """Extracted setting metadata for catalog serialization.
 
     This is the resolved form of a `Setting`, with all types inferred and
-    ready for serialization. See [`_SpecBase`][vgi.catalog._descriptor_spec._SpecBase]
+    ready for serialization. See `_SpecBase` (in `vgi.catalog._descriptor_spec`)
     for the field and wire-format definition.
     """
 
@@ -34,7 +34,7 @@ class Setting(_DescriptorBase):
 
     Use with `Annotated` type hints to declare settings in a [`Worker`][]'s Settings class.
     The Arrow type is resolved from the base type in the `Annotated` hint. See
-    [`_DescriptorBase`][vgi.catalog._descriptor_spec._DescriptorBase] for the
+    `_DescriptorBase` (in `vgi.catalog._descriptor_spec`) for the
     ``desc`` and ``arrow_type`` attributes.
     """