fix(losses): add missing docstring entries for default parameters (#8755)

## Description

Fixes missing and incomplete docstring parameter documentation in two
loss files, consistent with the pattern established in #8701.

### Changes

**`monai/losses/hausdorff_loss.py`**
- `HausdorffDTLoss.__init__`: Added missing `alpha` parameter (default
`2.0`) to the `Args` section. The parameter was present in the function
signature but completely absent from the docstring.

**`monai/losses/cldice.py`**
- `SoftclDiceLoss.__init__`: Added `Defaults to X.` to `iter_` and
`smooth` parameter descriptions.
- `SoftDiceclDiceLoss.__init__`: Added `Defaults to X.` to `iter_`,
`smooth`, and `alpha` parameter descriptions.

### Motivation

These are pure docstring fixes — no code logic was changed. The missing
`alpha` documentation in `HausdorffDTLoss` is the primary fix, and the
`cldice.py` changes follow the same "document defaults" pattern from
#8701.

## Checklist
- [x] Docstring-only change (no logic modified)
- [x] No new tests required
- [x] DCO sign-off included

---------

Signed-off-by: Shiran Yu <shiran.yu@bristol.ac.uk>
Signed-off-by: Eric Kerfoot <17726042+ericspod@users.noreply.github.com>
Co-authored-by: Eric Kerfoot <17726042+ericspod@users.noreply.github.com>
Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>

Author: 3 people

monai/losses/cldice.py

@@ -126,8 +126,8 @@ class SoftclDiceLoss(_Loss):
     def __init__(self, iter_: int = 3, smooth: float = 1.0) -> None:
         """
         Args:
-            iter_: Number of iterations for skeletonization
-            smooth: Smoothing parameter
+            iter_: Number of iterations for skeletonization. Defaults to 3.
+            smooth: Smoothing parameter. Defaults to 1.0.
         """
         super().__init__()
         self.iter = iter_
@@ -160,9 +160,9 @@ class SoftDiceclDiceLoss(_Loss):
     def __init__(self, iter_: int = 3, alpha: float = 0.5, smooth: float = 1.0) -> None:
         """
         Args:
-            iter_: Number of iterations for skeletonization
-            smooth: Smoothing parameter
-            alpha: Weighing factor for cldice
+            iter_: Number of iterations for skeletonization. Defaults to 3.
+            alpha: Weighing factor for cldice. Defaults to 0.5.
+            smooth: Smoothing parameter. Defaults to 1.0.
         """
         super().__init__()
         self.iter = iter_

monai/losses/hausdorff_loss.py

@@ -54,6 +54,7 @@ def __init__(
     ) -> None:
         """
         Args:
+            alpha: the exponent to transform the distance when computing the loss. Defaults to 2.0.
             include_background: if False, channel index 0 (background category) is excluded from the calculation.
                 if the non-background segmentations are small compared to the total image size they can get overwhelmed
                 by the signal from the background so excluding it in such cases helps convergence.