fix(chat): scope copy button to message content bubble only

[Gourav-InfoTech]

Description

Fixes the copy button appearing on all assistant message types. It now only appears on messages with text content, positioned inside the content bubble, and copies exactly the displayed text.

Changes

• Moved FloatingActions (copy button) inside a relative wrapper around MessageContent so it is scoped to the text bubble
• Copy button no longer renders on messages that have only tool executions (no text content)
• Copy action now uses cleanContent (follow-up questions and "Sources:" lines stripped) instead of raw message.content, matching what is actually visible
• Added copyContent prop to FloatingActions to control copied text and button visibility

Type of Change

• Bug fix (non-breaking change that fixes an issue)

Testing

• I've tested this locally

Manual test cases:

• Text-only assistant message → copy button appears on hover inside the bubble, copies correctly
• Message with only tool calls (no text) → copy button does not appear
• Message with both text and tool calls → copy button appears on the text bubble only
• Copied text does not include follow-up question markers or "Sources:" lines

Checklist

• My code follows the project's style guidelines
• New and existing tests pass locally

[vercel]

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