Document .NET 11 breaking change: correctly rounded Decimal/BigInteger floating-point conversions

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.NET 11 Preview 7 makes conversions between Decimal and binary floating-point types (float/double), and conversions from BigInteger to binary floating-point types, correctly rounded. Previously these conversions could truncate, round through intermediate values, or discard significant digits, producing results that differ from the true nearest representable value.

New breaking-change article

• Added docs/core/compatibility/core-libraries/11/decimal-biginteger-floating-point-conversions.md covering previous vs. new behavior, reason for change (with links to the originating dotnet/runtime PRs), recommended action, and the full list of affected APIs.

Index and navigation

• Added the article to docs/core/compatibility/toc.yml under Core .NET libraries → 11.
• Added a row for it in the Core .NET libraries table in docs/core/compatibility/11.md.

Related docs

• Added a cross-reference note in docs/csharp/language-reference/builtin-types/numeric-conversions.md where decimal ↔ float/double conversion behavior is described.

Example from the article illustrating the behavior change:

double value = 1.23;
decimal converted = (decimal)value;
// Previously: 1.23
// Now: 1.229999999999999982236431606 (the exact value of the double)

• Fixes [Breaking change]: Decimal and BigInteger floating-point conversions are correctly rounded #55743

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Internal previews

File	Preview link
docs/core/compatibility/11.md	Learn preview
docs/core/compatibility/core-libraries/11/decimal-biginteger-floating-point-conversions.md	Learn preview
docs/core/compatibility/toc.yml	Learn preview
docs/csharp/language-reference/builtin-types/numeric-conversions.md	Learn preview

Build report

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[gewarren]

Suggested change

	- <xref:System.Decimal.%23ctor(System.Single)?displayProperty=nameWithType>
	- <xref:System.Decimal.%23ctor(System.Double)?displayProperty=nameWithType>
	- <xref:System.Decimal.%23ctor(System.Single)>
	- <xref:System.Decimal.%23ctor(System.Double)>