[WIP] Fix docblock argument names and clarify usage context

[Copilot]

Cloud agent has begun work on The docblocks for im... and will update this pull request as work progresses.

Original prompt

The docblocks for image/json/text in the LanguageModelData part refer to a mimeType argument, but the argument is actually mime.

Also, the docblock for the class says it's "returned from a LanguageModelChatResponse", but this is not the only place the data is used, I suggest rewording or elaborating

The user has attached the following files as relevant context:

• .github/instructions/learnings.instructions.md
• .github/copilot-instructions.md

Created from VS Code via the GitHub Pull Request extension.

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