Add regression tests for numeric literal visitors (#128) (#158)

## Summary

Issue #128 reported a `System.FormatException` when converting binary
int constants such as `0b10`. **That crash is already fixed on master**
— commit 9957153 ("Support binary literals, #83") landed after the 3.0.0
build the reporter was using.

Verified with the reporter's exact snippet through the CLI:

```java
static final int FLAG_LONG_FRAME = 0b10;
static final int FLAG_COMMAND_FRAME = 0b100;
```

converts cleanly to:

```csharp
static readonly int FLAG_LONG_FRAME = 0b10;
static readonly int FLAG_COMMAND_FRAME = 0b100;
```

## Why this PR

The binary literal path only had indirect coverage via the
`BinaryLiterals.java` integration test, and only for local variables —
never for fields, and never at the visitor level.
`IntegerLiteralExpressionVisitor` and `LongLiteralExpressionVisitor` had
no direct unit tests at all.

This adds two theories covering both visitors across every base they
handle:

- binary, including uppercase `0B` and underscore separators
(`0b1_0000`)
- hex (`0x1F`)
- octal (`010`)
- decimal

No production code changes. This PR is test-only coverage; #128 can be
closed as already fixed.

## Test plan

- [x] `dotnet test` — 284 passed, 0 failed

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: paulirwin

JavaToCSharp.Tests/VisitLiteralExpressionTests.cs

@@ -18,5 +18,30 @@ public void VisitLiteralExpression_String()
         var expr = ExpressionVisitor.VisitExpression(new ConversionContext(new JavaConversionOptions()), new StringLiteralExpr(@"\\r"));
         Assert.Equal("\\r", expr?.GetFirstToken().ValueText);
     }
+
+    [Theory]
+    [InlineData("0b10", 2)]
+    [InlineData("0b100", 4)]
+    [InlineData("0B1010", 10)]
+    [InlineData("0b1_0000", 16)]
+    [InlineData("0x1F", 31)]
+    [InlineData("010", 8)]
+    [InlineData("42", 42)]
+    public void VisitLiteralExpression_Integer(string javaLiteral, int expected)
+    {
+        var expr = ExpressionVisitor.VisitExpression(new ConversionContext(new JavaConversionOptions()), new IntegerLiteralExpr(javaLiteral));
+        Assert.Equal(expected, expr?.GetFirstToken().Value);
+    }
+
+    [Theory]
+    [InlineData("0b10L", 2L)]
+    [InlineData("0B1010L", 10L)]
+    [InlineData("0x1FL", 31L)]
+    [InlineData("010L", 8L)]
+    public void VisitLiteralExpression_Long(string javaLiteral, long expected)
+    {
+        var expr = ExpressionVisitor.VisitExpression(new ConversionContext(new JavaConversionOptions()), new LongLiteralExpr(javaLiteral));
+        Assert.Equal(expected, expr?.GetFirstToken().Value);
+    }
 }