Docment renderers collapse parameterized annotations to their unparameterized type

Docment-based signature rendering loses type parameters from generic annotations.

For example, `list[str]` is rendered as `list`, and `tuple[str, int]` is rendered as `tuple`.

## Reproduction

```python
from fastcore.docments import sig2str

def f(
items:list[str],
) -> tuple[str, int]:
pass

print(sig2str(f))
```

Actual output:

```python
def f(
items:list
)->tuple:
```

Expected output:

```python
def f(
items:list[str]
)->tuple[str,int]:
```

## Environment

- fastcore: 2.2.13
- Branch: `main`

## Scope

The issue affects multiple docment renderers, including:

- `DocmentText`
- `DocmentList`
- `DocmentTbl`

## Likely cause

The renderers use `_maybe_nm()` for annotations:

```python
def _maybe_nm(o):
if o == inspect._empty: return ''
return o.__name__ if hasattr(o, '__name__') else str(o)
```

Parameterized generic aliases expose the unparameterized origin through `__name__`:

```python
tuple[str, int].__name__
# 'tuple'
```

By comparison, annotation-aware formatting preserves the parameters:

```python
inspect.formatannotation(tuple[str, int])
# 'tuple[str, int]'
```

Annotation formatting should preserve generic parameters without changing the existing formatting of ordinary classes or default values.

Start in fastcore.docments at _maybe_nm() and trace how DocmentText, DocmentList, and DocmentTbl format annotations for sig2str. Run the supplied reproduction with list[str] and tuple[str, int], then verify that generic parameters are preserved while ordinary classes and default values retain their existing formatting.

Written by the indexing model from the issue text.