feat(chat): group consecutive read tool messages

[ctlai95]

Problem

LLM will sometimes try to execute the fsRead tool (and listDirectory tool) many times in succession, when this happens we don't want to show every read message.

Solution

Update the existing chat message that already shows a read message if it exists.

Detailed changes

• Added a new type of UiMessage ToolMessage specifically for handling tool chat messages
• ToolMessage will call MynahUI's updateChatAnswerWithMessageId API
• For every "group" of consecutive read messages we store the first occurrence of the read tool's toolUseId in session storage and use that as the messageId to update
• Updated ChatStream class to take in this messageId to update for the current message

chat.mov

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[github-actions]

• This pull request modifies code in src/* but no tests were added/updated.
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