Refactor GUI to be more modular

[OpenSauce]

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[Copilot]

Pull Request Overview

This PR refactors the GUI into modular pieces by extracting configs, messages, and view components, and replaces the old monolithic amp.rs with a new AmplifierApp.

• Reorganized module structure under src/gui
• Introduced per-stage config and message modules
• Created reusable widget and stage view components

Reviewed Changes

Copilot reviewed 23 out of 24 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/gui/mod.rs	Updated root module to export app, components, config, and messages
src/gui/messages.rs	Extracted all GUI message enums into a dedicated module
src/gui/config/*.rs	Added individual config modules (filter, preamp, etc.) each with to_stage
src/gui/components/widgets/common.rs	Refactored common widget imports and cleaned up labeled_slider layout
src/gui/components/stages/*.rs	Moved each stage’s UI into its own view function in separate files
src/gui/components/stage_list.rs	Added StageList component to render the list of stages
src/gui/components/control.rs	Added Control component for stage type selection and adding stages
src/gui/app.rs	Introduced AmplifierApp and build_amplifier_chain logic
src/gui/amp.rs	Removed the old, monolithic GUI implementation file

Comments suppressed due to low confidence (4)

src/gui/app.rs:182

• Stage names passed to to_stage are inconsistent with display names (no space in ToneStack). Consider using "Tone Stack {idx}" to match the user-facing label.

                    cfg.to_stage(&format!("ToneStack {idx}"), sample_rate),

src/gui/config/preamp.rs:21

• [nitpick] The to_stage method for PreampConfig omits a sample_rate parameter, unlike other configs. Consider standardizing all to_stage signatures to accept sample_rate for consistency.

    pub fn to_stage(&self, name: &str) -> PreampStage {

src/gui/config/tonestack.rs:1

• [nitpick] Consider adding unit tests for ToneStackConfig::to_stage to verify that it constructs a ToneStackStage with correct default and custom parameters.

use crate::sim::stages::tonestack::{ToneStackModel, ToneStackStage};

src/gui/components/stages/tonestack.rs:20

• The model_picker row is missing .spacing() and .align_y() modifiers, which may break its layout. Add .spacing(10).align_y(Alignment::Center) to match other stage pickers.

    let model_picker = row![