Description of the bug

signature_crossrefs is creating links from local variables used to set instance attributes, where the docs say that it should only be doing it for type annotations.

This becomes a problem if the local variable name matches the name of a heading somewhere else in the docs.

To Reproduce

Setup:

pip install mkdocs-material mkdocs-api-autonav
touch mkdocs.yml
mkdir docs
touch docs/index.md
mkdir src
touch src/__init__.py

# mkdocs.yml
site_name: Docs
theme:
  name: material
plugins:
  - autorefs
  - mkdocstrings:
      handlers:
        python:
          options:
            show_if_no_docstring: true
            separate_signature: true
            signature_crossrefs: true
  - api-autonav:
      modules: ["src"]

<!-- docs/index.md -->
# Intro

# src/__init__.py
class Class:
    def __init__(self):
        intro = "Some text"
        self.attr = intro

Finally:

• run mkdocs serve
• open http://127.0.0.1:8000/reference/src/
• notice that:
  • intro has become a link
  • that link takes you to http://127.0.0.1:8000/#intro, which is unrelated

Expected behavior

This link should not have been created.

Environment information

• System: macOS-26.1-arm64-arm-64bit
• Python: cpython 3.12.8 (~/.venv/bin/python)
• Environment variables:
• Installed packages:
  • mkdocstrings-python v1.19.0