fix: unrelated struct with that shape can be misclassified

[Azhovan]

What

• Tighten optional detection in binding.go so only rigging.Optional[T] is treated as optional.
• Add regression coverage in binding_bind_test.go to ensure lookalike structs (Value + Set bool) are handled as normal nested structs.

Why

Structural detection could misclassify unrelated structs, causing nested fields to be skipped during binding. This fix prevents silent misbinding and keeps optional semantics scoped to the intended type.

Type

• Fix
• Feature
• Docs
• Performance
• Breaking change

Testing

Verified with formatting, targeted regression checks, full test suite, vet, and coverage:

gofmt -w binding.go binding_bind_test.go
go test ./... -run 'TestBindStruct_ValueSetLookalikeStructIsNotOptional|TestBindStruct_OptionalField|TestBinding_ConvertValue_Optional'
go test ./...
go vet ./...
go test -coverprofile=coverage.out ./... && go tool cover -func=coverage.out | tail -n 1

[Copilot]

Pull request overview

This PR fixes a bug where user-defined structs with Value and Set bool fields could be incorrectly identified as rigging.Optional[T] types, causing nested fields to be skipped during binding. The fix adds package path and type name checks to the isOptionalType function, ensuring only actual rigging.Optional[T] types are treated as optional.

Changes:

• Enhanced isOptionalType() with package path and type name prefix validation to prevent misclassification
• Added regression test to verify lookalike structs are properly handled as nested structs

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
binding.go	Added optionalTypePkgPath variable and strengthened isOptionalType() with package path and name checks
binding_bind_test.go	Added TestBindStruct_ValueSetLookalikeStructIsNotOptional to verify lookalike structs bind correctly as nested types

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