Document generated plugin user names

[gabek]

The SDK already omits displayName for its shorthand registration call, but its JavaScript type rejected an explicit null.

• Allow displayName: null in the JavaScript request type.
• Document that omitted or null names are generated by Owncast in both SDK references.
• Clarify the equivalent Python display_name=None behavior.
• Update the host runtime dependency so example CI can build against the matching Owncast branch.

Requires owncast/owncast#5112 for the host behavior.

$ node --check sdks/js/index.js
$ python3 -m py_compile sdks/python/owncast_plugin/__init__.py
$ GOTOOLCHAIN=go1.26.2 GOPROXY=off go test ./...
go test: 3 packages ok, 2 no tests

[Copilot]

Pull request overview

This PR updates the SDK documentation and JavaScript typings to explicitly support generated user display names when displayName/display_name is omitted (and, for JS/wire protocol, when it is null). This aligns SDK references with the host behavior described in the PR description.

Changes:

• Allow displayName: null in the JavaScript UserRegisterRequest type.
• Document in the wire protocol and author guide that omitted/null displayName causes Owncast to generate a name.
• Update the Python SDK docstring for users.register to describe generated-name behavior when display_name is omitted.

Reviewed changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated 2 comments.

File	Description
sdks/python/owncast_plugin/__init__.py	Updates users.register docstring to describe generated names when display_name is omitted.
sdks/js/index.d.ts	Expands UserRegisterRequest.displayName to `string
docs/WIRE_PROTOCOL.md	Documents displayName as optional+nullable and updates UserRegisterRequest type accordingly.
docs/PLUGIN_AUTHOR_GUIDE.md	Adds narrative documentation that displayName may be omitted or null to generate a name.

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