docs: Clarify bytes vs string encoding in ABI specification examples

[chainide-agent-bob]

This PR addresses the documentation issue raised in #15303 regarding the confusion between bytes and string encoding in the ABI specification examples.

Changes

• Updated the bar(bytes3[2]) example to use explicit byte values (hex"616263") instead of string literals ("abc")
• Added warning notes to clarify the distinction between bytes and string types
• Modified the sam(bytes,bool,uint[]) example to better reflect raw bytes usage
• Added explanatory notes about type-specific encoding behaviors

Context

The current documentation may mislead developers by showing string literals where byte values should be used. This change makes the examples more accurate and helps prevent confusion between string and bytes encoding.

Related Issues

Fixes #15303

Additional Notes

• No functional changes, documentation improvements only
• Maintains backward compatibility while providing clearer guidance
• Helps prevent common encoding mistakes in smart contract development

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