Add MDN documentation links to generated WebAPI bindings

[Copilot]

Generated MoonBit bindings lack documentation linking to MDN Web API references, making it harder for developers to understand the underlying Web Platform APIs.

Changes

• MDN URL helpers (emit.mbt): Added mdn_interface_url and mdn_member_url functions to construct MDN documentation URLs
• Interface type docs: Emit::External now emits doc comments with MDN links for interface types
• Trait definition docs: Emit::InterfaceDefinition includes MDN links for trait definitions
• Method/attribute docs: Updated all method emitters (RegularMethodEmit, StaticMethodEmit, AttributeGetMethodEmit, AttributeSetMethodEmit, StaticAttributeGetMethodEmit) to include MDN links
• Test snapshots: Updated all interface emitter tests to expect new doc format

Example

After running make gen, generated code will include:

/// [HTMLImageElement](https://developer.mozilla.org/en-US/docs/Web/API/HTMLImageElement)
#external
pub type HTMLImageElement

/// [HTMLImageElement](https://developer.mozilla.org/en-US/docs/Web/API/HTMLImageElement) interface.
pub trait THTMLImageElement: THTMLElement {
  src(self : Self) -> String = _
}

/// [HTMLImageElement.src](https://developer.mozilla.org/en-US/docs/Web/API/HTMLImageElement/src)
impl THTMLImageElement with src(self : Self) -> String {
  html_image_element_src_ffi(TJsValue::to_js(self))
}

Run make gen to regenerate bindings with documentation links.

Warning

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• download.mooncakes.io
  • Triggering command: /home/REDACTED/.moon/bin/moon moon check --target js (dns block)
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Original prompt

For each idl interface method/attribute, I wan to add moonbit documentation that points to mdn documentation. For examples https://github.com/bikallem/webapi/blob/main/src/html_image_element_interface.mbt should point to https://developer.mozilla.org/en-US/docs/Web/API/HTMLImageElement. Investigate how we can do this and create an implementation plan.

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[Copilot]

Pull request overview

This PR adds MDN documentation links to generated MoonBit bindings for Web Platform APIs, improving developer experience by providing easy access to Web API reference documentation.

• Adds helper functions to construct MDN documentation URLs
• Updates all interface method and type emitters to include MDN doc comments
• Updates test snapshots in interface_emitter_wbtest.mbt to reflect new documentation format

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
webapi_gen/emit/emit.mbt	Adds mdn_interface_url and mdn_member_url helper functions; updates External type and InterfaceDefinition emitters to include MDN doc comments
webapi_gen/emit/interface_method_emit.mbt	Updates all five method emitters (RegularMethodEmit, StaticMethodEmit, AttributeGetMethodEmit, AttributeSetMethodEmit, StaticAttributeGetMethodEmit) to emit MDN documentation links for methods and attributes
webapi_gen/emit/interface_emitter_wbtest.mbt	Updates all test snapshots to expect new MDN documentation format in generated code

[Copilot]

The current implementation adds MDN documentation links to all External types, including synthetic union types that don't exist in MDN. For example, TestInterfaceTestMethodParam2 is a generated type name for nested union types like (unsigned long or boolean), not an actual Web API interface.

These synthetic union types are created by the code generator at line 594 in emit.mbt when processing nested unions. They should not include MDN documentation links since they don't correspond to any Web API documentation.

Consider:

1. Adding a flag or variant to the Emit::External type to distinguish between real Web API interfaces and synthetic union types
2. Only emitting MDN documentation for External types that correspond to actual WebIDL interfaces, callbacks, or dictionaries (not synthetic union types)
3. Alternatively, use a different naming pattern for synthetic union types that makes it clear they shouldn't have MDN links

Suggested change

	let mdn_url = mdn_interface_url(type_name)
	buf.write_string("/// [\{type_name}](\{mdn_url})\n#external\npub type \{type_name}")
	buf.write_string("/// \{type_name}\n#external\npub type \{type_name}")