Fix Sphinx API documentation warnings

[contromo]

Summary

• resolve class-scoped unfreezable type aliases in generated method signatures
• render Napoleon attribute documentation as instance-variable fields to prevent duplicate object registrations
• fix malformed RST in the Conv1d math docstring

Relationship to #1

This branch is based directly on main and can be reviewed independently. PR #1 fixes the remaining narrative-document and Codon warnings; the two branches together pass a strict Sphinx build.

Validation

• reduced API documentation build: no unresolved type-reference, duplicate-object, or Conv1d RST warnings
• combined with Refresh documentation for v1.5 and fix examples and references #1: sphinx-build -W --keep-going passes with the Git LFS notebook sources excluded locally
• test suite: 532 passed, 20 skipped, 11 deselected; the two failing Conv1d gauge tests reproduce unchanged on main
• mypy and Black results match main (no new findings)