fix(v2): preserve nested struct JSON structure for embedded types with json tags

[leaanthony]

Summary

Fixes #4117

When a Go struct has anonymous embedded struct fields with explicit json tags (e.g., TimeLimitDef \json:"timeLimitDef"`), Go's encoding/json` marshals them as nested objects. However, the TS binding generator unconditionally flattened these fields, producing incorrect TypeScript that couldn't deserialize the JSON.

Changes

• deepFields() in typescriptify.go: Check for json tags on anonymous fields before flattening. If an anonymous field has an explicit json tag name, treat it as a regular struct field.
• AddStructToGenerateTS() in binding.go: Register embedded struct types with json tags for separate TS class generation instead of skipping them.
• New test binding_embedded_named_struct_jsontag_test.go that reproduces the exact scenario from the bug report.

Before (buggy)

export class LicenseCreateEntity {
    name: string;
    typ: string;
    desc: string;
    isInfinite: boolean;    // Flattened!
    startTime: number;      // Flattened!
    endTime: number;        // Flattened!
    appName: string;        // Flattened!
    ...
}

After (fixed)

export class LicenseCreateEntity {
    name: string;
    typ: string;
    desc: string;
    timeLimitDef: TimeLimitDef;   // Nested!
    application: Application;      // Nested!
}

Test plan

• All existing binding tests pass (no regressions)
• New test EmbeddedNamedStructJSONTagTest passes with correct nested output
• Verify generated TS bindings work with actual Go JSON serialization

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[leaanthony]

🤖 PR Triage Review

✅ Accepted

Preserves nested struct JSON structure for embedded types with json tags (v2 bindings). Improves JSON handling.

Platform: All (v2, bindings)

Next Steps: Dispatching for testing on all platforms.

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Reviewed by Wails PR Reviewer Bot

[taliesin-ai]

Duplicate of #5221 — same embedded-struct JSON/TS generation fix; consolidating on #5221. Closing this one and keeping #5221.