test(syntax): harden probes and align support status

[Jim8y]

Summary

• fail syntax probes on unexpected compiler exceptions instead of treating arbitrary crashes as success
• evaluate syntax probes against the contract unsupported-syntax analyzer so docs reflect real Neo contract acceptance
• remove the ambiguous compile-only status from syntax documentation and probe metadata
• classify top-level statements and file-local types as unsupported because the contract analyzer rejects them
• keep collection expressions supported for explicit-element forms and split spread elements into a dedicated unsupported syntax entry
• keep controlled diagnostics for unsupported collection-expression spread and setterless assignment paths

Review Notes

• top-level statements are not deployable contract surface and should remain unsupported
• file-local types are currently blocked by the analyzer and should remain unsupported until there is an explicit support decision
• collection expressions already have runtime coverage for array, jagged-array, byte-array, and Neo framework list forms, so those forms should stay supported
• spread elements remain a real implementation gap and should be tracked explicitly as unsupported instead of hidden behind a mixed-status umbrella entry

Testing

• dotnet test tests/Neo.Compiler.CSharp.UnitTests/Neo.Compiler.CSharp.UnitTests.csproj -c Release --nologo
• dotnet test tests/Neo.Compiler.CSharp.UnitTests/Neo.Compiler.CSharp.UnitTests.csproj -c Release --nologo --filter "FullyQualifiedNameNeo.Compiler.CSharp.UnitTests.Syntax.SyntaxTests|FullyQualifiedNameUnitTest_CollectionExpressionSupport|FullyQualifiedName~UnitTest_Array.Test_Collectionexpressions"

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 73.87%. Comparing base (9a44c4b) to head (4d5484e).

Additional details and impacted files

@@              Coverage Diff              @@
##           master-n3    #1573      +/-   ##
=============================================
- Coverage      80.26%   73.87%   -6.40%     
=============================================
  Files            295      326      +31     
  Lines          25436    27904    +2468     
  Branches        3454     3778     +324     
=============================================
+ Hits           20417    20614     +197     
- Misses          4121     6386    +2265     
- Partials         898      904       +6     

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