Version equality uses hashes instead of version data

## Reproduction

Reproduced on `main` at `1b70bf6c9d988fb200ae506676ad1e8f5f1b644a`.

```python
from concoursetools import Version

class FileVersion(Version):
def __init__(self, path):
self.path = path

def __hash__(self):
return 42 # Force a collision for a deterministic reproduction

first, second = FileVersion("one"), FileVersion("two")
print(first == second) # True, despite different version data
print(first == 42) # True, but an integer is not a version
print(first == []) # TypeError: unhashable type: 'list'
```

`Version.__eq__` compares only hashes. Two different versions with the same hash also compare equal, so a set or dictionary can discard a distinct version. This can be reproduced deterministically with a `FileVersion` subclass whose `__hash__` returns a constant.

## Expected

Equality should compare the version type and flattened version data. Unrelated objects should be handled through `NotImplemented`, without attempting to hash them.

I have reproduced this and am preparing a focused fix with regression tests.

Start by inspecting Version.__eq__ and the Version data-flattening behavior described in the reproduction. Add regression tests covering hash collisions, unrelated objects, and unhashable objects; done means equality uses version type and flattened data without hashing unrelated values.

Written by the indexing model from the issue text.