Fix unresolved-any converter re-entry during style computation

[sebastienros]

Types of Changes

Prerequisites

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• Bug fix (non-breaking change which fixes an issue, please reference the issue id)
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Description

ComputeCurrentStyle() stack-overflows on a plain <div style='translate: 1px'></div>. The same issue affects rotate and scale: their composite converters accept opaque tokens through an Any arm, then CssAnyValue.Compute recursively recomputes the returned CssAnyValue through the same converter. No JavaScript or custom-property cycle is needed; the re-entry predates #242.

After checking that conversion consumed the complete input, return an accepted CssAnyValue directly. Concrete results still compute normally, and direct Any / missing-converter IsResolved behavior remains unchanged. This is a computation-boundary fix, not a property-specific workaround; #242's custom-property resolution and cycle handling are untouched.

Fixes: #243

Regression coverage includes translate 1/2/3-component forms, percentages and zero, rotate/scale and none, nested composite converters, concrete unit/calc conversion, invalid/trailing input, exception propagation, render-tree and specified-style compatibility, substitution, inheritance, and missing/cyclic variable fallback behavior.

Validation

• Exact native repro with AngleSharp 1.8.0 and published AngleSharp.Css 1.1.0, plus unmodified devel source: process stack overflow before the fix. Fixed source and a uniquely versioned local diagnostic package both print 1px on .NET 8 and .NET 10.
• Focused suites: 140 passed on each runtime.
• Full suites: 2,269 passed on each runtime, both with the default AngleSharp dependency and with AngleSharp 1.8.0.
• Release library builds for netstandard2.0, net8.0, and net10.0 passed without warnings or errors. Final validation used SDK 10.0.400; .NET 10 tests used -p:TargetFrameworks=net10.0 -p:RestoreEnablePackagePruning=false without changing project manifests.

Scope

Existing individual-transform Any grammars remain permissive and retain token serialization; this does not add grammar validation, browser-style unit normalization, or transform layout. Windows-only net462/net472 targets were not exercised on macOS. No public API, dependency, or package-version changes are included.

[FlorianRappl]

LGTM!