M3 expressive wavy progress indicators

[dfabulich]

Fixes #379

This PR upgrades us to androidx-material3 1.5.0-alpha16, so we can access the new M3 Expressive stuff.

I've added a new .material3WavyProgress() modifier. You can pass it no arguments, and it will do the right thing, or you can configure the amplitude, wavelength, and "wave speed"

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  M3 expressive wavy progress indicators skipapp-showcase#85

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• AI was used to generate or assist with generating this PR. Please specify below how you used AI to help you, and what steps you have taken to manually verify the changes.

Cursor generated a first draft, which I manually cleaned up and documented. I manually tested the new progress indicators in the ProgressViewPlayground in both the Lite and Fuse showcases.

Before / After

Screen_recording_20260401_200124.webm

[marcprux]

The implementation looks solid, but unless you have an urgent need for it, I'd like to hold off on this at least until androidx-material3 comes out of alpha (which hopefully will be soon, singe they're on 1.5.0-alpha16 now).

Another issue I'd like to consider for this sort of thing is whether it might be better to extend the progressViewStyle() values rather than having an Android-specific method for this, which might align somewhat better with SwiftUI patterns. So like:

ProgressView()
    #if os(iOS)
    .progressViewStyle(.linear)
    #elseif os(Android)
    .progressViewStyle(.material3Wavy(gapSize: 2.0, amplitude: 1.0))
    #endif

[dfabulich]

I went with a separate modifier for two reasons.

First, because wavy is a mode on top of a style; you can choose either linear-wavy or circular-wavy.

ProgressView()
    .progressViewStyle(.linear)
    #if os(Android)
    .material3WavyProgress()
    #endif
    
ProgressView()
    .progressViewStyle(.circular)
    #if os(Android)
    .material3WavyProgress()
    #endif

Second, it means that I could set .material3WavyProgress() at the top level of my app, and it turned all of my progress indicators wavy.

If we did it with separate .progressViewStyles:

ProgressView()
    #if os(Android)
    .progressViewStyle(.material3WavyLinear)
    #else
    .progressViewStyle(.linear)
    #endif
    
ProgressView()
    #if os(Android)
    .progressViewStyle(.material3WavyCircular)
    #else
    .progressViewStyle(.circular)
    #endif

… and I'd have to wire that up everywhere in my entire app.

I think .progressViewStyle might be appropriate for the new animated "morphing" indicator, LoadingIndicator

• M3 expressive indeterminate morphing loading indicator #395

LoadingIndicator is round-ish, so it's more like a circular indeterminate progress indicator, but it's intended for "permanently indeterminate" loading indicators.