`MarkdownRenderer.__repr__` places the docstring inside a return-docment comment

When a function has both a docstring and a trailing docment on its return annotation, `MarkdownRenderer.__repr__` appends the docstring directly after the rendered signature.

Because the signature ends with an inline `#` comment, the docstring becomes part of that comment instead of appearing as the function body.

This is visible through `pyskills.doc()`, which uses `MarkdownRenderer`.

## Reproduction

```python
from pyskills import doc

def f() -> int: # return value
"docstring"

doc(f)
```

Actual output:

```python
def f()->int: # return value"""docstring"""
```

Expected output:

```python
def f()->int: # return value
"""docstring"""
```

A direct fastcore reproduction is:

```python
from fastcore.docments import MarkdownRenderer

def f() -> int: # return value
"docstring"

repr(MarkdownRenderer(f))
```

## Impact

The rendered result is misleading and is not valid as a representation of the original function body: everything after `# return value` is part of the comment.

The issue occurs whenever all three conditions are present:

1. The function has a docstring.
2. The return annotation has a trailing docment.
3. The plain-text representation of `MarkdownRenderer` is used.

## Environment

- fastcore: 2.2.13
- Branch: `main`

## Likely cause

`MarkdownRenderer.__repr__` concatenates the docstring directly onto the rendered `DocmentText`:

```python
def __repr__(self):
doc = str(self.dm)
if self.docs: doc += f'"""{self.docs}"""'
return doc
```

When `str(self.dm)` ends with a return docment, it ends in an inline comment:

```python
)->int: # return value
```

Appending the docstring without a newline places it inside that comment.

The renderer should insert a newline and indentation before the docstring, including appropriate indentation for multiline docstrings.

Start at MarkdownRenderer.__repr__ and reproduce the issue with the fastcore example or through pyskills.doc(). Trace how str(self.dm) is combined with self.docs. Done means the docstring appears on a new, indented line after the return comment, including suitable indentation for multiline docstrings, without changing the rendered signature.

Written by the indexing model from the issue text.