## `parse_tag()` raises `ValueError` instead of `InvalidTag` for tags with wrong number of components

### Description

Calling `parse_tag()` with a tag string that doesn't have exactly three hyphen-separated components (interpreter, ABI, platform) raises a raw `ValueError` from Python's tuple unpacking instead of the documented `InvalidTag` exception.

For example:

```python
from packaging import tags

# Tag with only two components (missing platform)
tags.parse_tag("py3-none")

# Tag with four components (extra field)
tags.parse_tag("py3-none-any-extra")
```

Running either of these raises:

```
ValueError: not enough values to unpack (expected 3, got 2)
```

or

```
ValueError: too many values to unpack (expected 3)
```

The error originates from the internal tuple unpacking `interpreters, abis, platforms = component_parts` in `parse_tag()` in `src/packaging/tags.py`.

### Expected behavior

Both inputs should raise `tags.InvalidTag` (a subclass of `ValueError`) with a message indicating the tag must have exactly three components, consistent with how empty tag components are already handled. Code that catches `InvalidTag` to handle malformed tags should not need to also catch the bare `ValueError`.

### Actual behavior

A plain `ValueError` is raised directly from the tuple unpacking, bypassing the `InvalidTag` public error contract. Any caller that catches `tags.InvalidTag` to validate tag strings will miss these malformed inputs.

Work in `/workspace`. Submit your fix in the existing Python source files under `src/packaging`. Preserve the other public behavior. The environment is offline; dependencies are preinstalled. Grading runs the repository's test suite in a fresh environment, using your submitted source files.