feat(docs): Support cross language "auto links" (#5699)

Introduces a syntax for cross-reference links that work across language
and change behavior depending on which scope they appear in.


```markdown
@[interrupt]

:::python
@[StateGraph]
:::

:::js
@[create_react_agent]
:::

```

Can be compiled to

```markdown

# a link that changes based on global context or compile target
<div> ... </div>  -> `interrupt` in global context

:::python
[StateGraph](link to python cross reference)
:::

:::js
[create_react_agent](link to js cross reference)
:::
```



TODO:

- [x] fix broken unit test
- [x] no f strings in logger (it's a sin)
- [x] remove cross-refs.txt (we'll instead start updating the cross link
map)

docs/tests/unit_tests/test_auto_links.py

@@ -0,0 +1,146 @@
+"""Unit tests for cross-reference preprocessing functionality."""
+
+from unittest.mock import patch
+
+import pytest
+
+from _scripts.handle_auto_links import _transform_link, _replace_autolinks
+
+
+@pytest.fixture
+def mock_link_maps():
+    """Fixture providing mock link maps for testing."""
+    mock_scope_maps = {
+        "python": {"py-link": "https://example.com/python"},
+        "js": {"js-link": "https://example.com/js"},
+    }
+
+    with patch("_scripts.handle_auto_links.SCOPE_LINK_MAPS", mock_scope_maps):
+        yield mock_scope_maps
+
+
+def test_transform_link_basic(mock_link_maps) -> None:
+    """Test basic link transformation."""
+    # Test with a known link
+    result = _transform_link("py-link", "python", "test.md", 1)
+    assert result == "[py-link](https://example.com/python)"
+
+    # Test with an unknown link (returns None)
+    result = _transform_link("unknown-link", "global", "test.md", 1)
+    assert result is None
+
+
+def test_no_cross_refs(mock_link_maps) -> None:
+    """Test markdown with no @[references]."""
+    lines = ["# Title\n", "Regular text.\n"]
+    markdown = "".join(lines)
+    result = _replace_autolinks(markdown, "test.md")
+    expected = "".join(["# Title\n", "Regular text.\n"])
+    assert result == expected
+
+
+def test_global_cross_refs(mock_link_maps) -> None:
+    """Test @[references] in global scope (no conditional blocks)."""
+    lines = ["@[global-link]\n", "Text with @[unknown-link].\n"]
+    markdown = "".join(lines)
+    result = _replace_autolinks(markdown, "test.md")
+    expected = "".join(["@[global-link]\n", "Text with @[unknown-link].\n"])
+    assert result == expected
+
+
+def test_python_conditional_block(mock_link_maps) -> None:
+    """Test @[references] inside Python conditional block."""
+    lines = [":::python\n", "@[py-link]\n", ":::\n"]
+    markdown = "".join(lines)
+    result = _replace_autolinks(markdown, "test.md")
+    expected = "".join(
+        [":::python\n", "[py-link](https://example.com/python)\n", ":::\n"]
+    )
+    assert result == expected
+
+
+def test_js_conditional_block(mock_link_maps) -> None:
+    """Test @[references] inside JavaScript conditional block."""
+    lines = [":::js\n", "@[js-link]\n", ":::\n"]
+    markdown = "".join(lines)
+    result = _replace_autolinks(markdown, "test.md")
+    expected = "".join([":::js\n", "[js-link](https://example.com/js)\n", ":::\n"])
+    assert result == expected
+
+
+def test_all_scopes(mock_link_maps) -> None:
+    """Test @[references] in global, Python, and JavaScript scopes."""
+    lines = [
+        "@[global-link]\n",
+        ":::python\n",
+        "@[py-link]\n",
+        ":::\n",
+        "@[global-link]\n",
+        ":::js\n",
+        "@[js-link]\n",
+        ":::\n",
+        "@[global-link]\n",
+    ]
+    markdown = "".join(lines)
+    result = _replace_autolinks(markdown, "test.md")
+    expected = "".join(
+        [
+            "@[global-link]\n",
+            ":::python\n",
+            "[py-link](https://example.com/python)\n",
+            ":::\n",
+            "@[global-link]\n",
+            ":::js\n",
+            "[js-link](https://example.com/js)\n",
+            ":::\n",
+            "@[global-link]\n",
+        ]
+    )
+    assert result == expected
+
+
+def test_fence_resets_to_global(mock_link_maps) -> None:
+    """Test that closing fence resets scope to global."""
+    lines = [":::python\n", "@[py-link]\n", ":::\n", "@[global-link]\n"]
+    markdown = "".join(lines)
+    result = _replace_autolinks(markdown, "test.md")
+    expected = "".join(
+        [
+            ":::python\n",
+            "[py-link](https://example.com/python)\n",
+            ":::\n",
+            "@[global-link]\n",
+        ]
+    )
+    assert result == expected
+
+
+def test_indented_conditional_fences(mock_link_maps) -> None:
+    """Test @[references] inside indented conditional fences (e.g., in tabs or admonitions)."""
+    lines = [
+        "@[global-link]\n",
+        "    :::python\n",
+        "    @[py-link]\n",
+        "    :::\n",
+        "@[global-link]\n",
+        "\t\t:::js\n",
+        "\t\t@[js-link]\n",
+        "\t\t:::\n",
+        "@[global-link]\n",
+    ]
+    markdown = "".join(lines)
+    result = _replace_autolinks(markdown, "test.md")
+    expected = "".join(
+        [
+            "@[global-link]\n",
+            "    :::python\n",
+            "    [py-link](https://example.com/python)\n",
+            "    :::\n",
+            "@[global-link]\n",
+            "\t\t:::js\n",
+            "\t\t[js-link](https://example.com/js)\n",
+            "\t\t:::\n",
+            "@[global-link]\n",
+        ]
+    )
+    assert result == expected