[python] adjust ipykernel raw_input docstring (#11069)

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#### New Features

- N/A

#### Bug Fixes

- #9640 Help calls for Python's builtin `input()` function include
explanation of `ipykernel.kernelbase.Kernel.raw_input` involvement.


### QA Notes

in the console

```python
help(input)
```

brings up info about why `raw_input` is being shown


<img width="468" height="331" alt="Screenshot 2025-12-11 at 5 09 31 PM"
src="https://github.com/user-attachments/assets/93b59b80-2a10-46f5-9bed-d29358b91884"
/>

Author: isabelizimm

extensions/positron-python/python_files/posit/positron/pydoc.py

@@ -42,6 +42,8 @@
 
 logger = logging.getLogger(__name__)
 
+BUILTIN_FUNCTIONS = ["input"]
+
 
 def _compact_signature(obj: Any, name="", max_chars=45) -> str | None:
     """
@@ -761,6 +763,11 @@ def _version_text(self, version: str) -> str:
 def _pydoc_getdoc(object_: Any) -> str:
     """Get the doc string or comments for an object."""
     result = inspect.getdoc(object_) or inspect.getcomments(object_)
+    try:
+        if object_.__qualname__ == "Kernel.raw_input" and result is not None:
+            result += _ipykernel_input_info()
+    except AttributeError:
+        pass
     return (result and re.sub("^ *\n", "", result.rstrip())) or ""
 
 
@@ -872,6 +879,8 @@ def _linkify_match(match: re.Match, object_: Any) -> str:
 
     # Try to resolve `target` and replace it with a link.
     key = _resolve(name, object_)
+    if name in BUILTIN_FUNCTIONS:
+        key = name
     if key is None:
         logger.debug("Could not resolve")
         return match.group(0)
@@ -974,6 +983,16 @@ def _url_handler(url: str, content_type="text/html"):
     raise TypeError(f"unknown content type {content_type!r} for url {url}")
 
 
+def _ipykernel_input_info() -> str:
+    """Adjust docstring for ipykernel.kernelbase.Kernel.raw_input."""
+    return """
+.. note::
+   When running in an IPython kernel, calls to the builtin function `input` are intercepted
+   and forwarded to the kernel's `raw_input` method, which communicates with
+   the frontend to request user input.
+"""
+
+
 def start_server(port: int = 0):
     """Adapted from pydoc.browser."""
     # Setting port to 0 will use an arbitrary port