Document that contract parameters can be mixed with contract-level constants

[Gusarich]

Minimal reproducible snippet:

contract Example(
    a: Int,
    b: Int
) {
    const DEFAULT: Int = 42; // contract parameter mixed with constant
}

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Actual behavior:

The compiler correctly accepts contracts declaring parameters alongside internal constants.

However, this valid combination is not mentioned in the documentation.

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Expected behavior:

The documentation currently states:

"The use of contract parameters syntax conflicts with using an init() function or declaring persistent state variables via the contract fields syntax."

But it does not explicitly mention that declaring contract-level constants alongside parameters is a valid and supported pattern.

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Why this matters:

• Explicitly documenting this valid behavior avoids confusion.
• Users currently might incorrectly assume that parameters and constants cannot be combined due to unclear documentation.

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Suggested fix:

• Update the documentation to clearly mention that contract parameters can be combined with internal constants, explicitly confirming that this is allowed and supported.

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LLM Fuzzing discovery (see #2490)

[spacejulesofficial-max]

This explanation is super clear! 🙌

Maybe it would help readers even more to include a small “before/after” code snippet or a short visual block in the docs — for example, showing how parameters and constants can coexist inside the same contract.

Something like:

contract Example(a: Int, b: Int) {
const DEFAULT: Int = 42;
// parameters and constants can live together
}

That way, new users can instantly see that this pattern is supported.

If helpful, I’d be happy to mock up a short visual or doc paragraph for this section.