fix: exclude localparams from parameter overrides

[hongjr03]

Summary

This change models parameter declarations in HIR as either parameter or localparam, including keyword inheritance in module parameter port lists.

Code actions and completion now use the HIR overridability model instead of treating all parameter declarations as instance-override candidates. This prevents Fill parameters from adding module-local localparam entries such as memory operation constants.

Validation

• cargo fmt --check
• cargo test -p ide code_action::tests
• cargo test -p ide completion::engine
• cargo test code_action_request_

[github-actions]

Docs preview: https://vide.pascal-lab.net/preview/pr-218/

[hongjr03]

Keeping this in draft while I revisit the parameter classification.

The current HIR model handles explicit localparam declarations and keyword inheritance inside the parameter port list, but it still needs to mirror the SystemVerilog/slang rule that when a module has a parameter port list, directly contained body parameter declarations are implicitly local and cannot be overridden by instance parameter assignments.