Add column width control and leading ellipsis truncation to Table widget

[StevenTCramer]

Current Behavior

The `TimeWarpTerminal.WriteTable()` widget automatically truncates all columns at the end with trailing ellipsis:
```
│ Path │
│ /home/steventcramer/worktrees/github.com/TimeWa... │
```

Desired Behavior

1. Column width control - Allow specifying max width per column (e.g., `.AddColumn("Path", maxWidth: 50)`)
2. Leading ellipsis truncation - For long paths, show ellipsis at the BEGINNING so the END (most significant part) is visible:
   ```
   │ Path │
   │ .../timewarp-ganda/Cramer-2025-12-06-dev │
   ```

Use Case

In worktree listings, the path is important but very long. Users need to see:

• Branch name (at the end of path)
• Repository name
• Just enough of the path to identify the worktree

With trailing ellipsis, all worktrees look the same because the unique part at the end is hidden.

Proposed API

```csharp
terminal.WriteTable(table =>
{
table
.AddColumn("Branch", Alignment.Left, maxWidth: 30)
.AddColumn("Repository", Alignment.Left, maxWidth: 20)
.AddColumn("Path", Alignment.Left, maxWidth: 50, truncation: Truncation.LeadingEllipsis);
});
```

Workaround Currently Used

Manually truncating strings before passing to the table:
```csharp
private static string TruncatePathLeading(string path, int maxLength)
{
if (path.Length <= maxLength) return path;
string end = path[(path.Length - maxLength + 3)..];
int sep = end.IndexOf(Path.DirectorySeparatorChar);
if (sep > 0) end = end[sep..];
return "..." + end;
}
```

This should be built into the library.

Labels

enhancement