fix(ui): suffix slider step literals to satisfy float_literal_f32_fallback

[OpenSauce]

Problem

CI's Lint job is failing on main and on every open PR (e.g. #264, a dependabot bump that has nothing to do with these files):

error: falling back to `f32` as the trait bound `f32: From<f64>` is not satisfied
   --> rustortion-ui/src/app.rs:549:23
    |
549 |                 .step(1.0),
    |                       ^^^ help: explicitly specify the type as `f32`: `1.0_f32`
    |
    = note: `-D float-literal-f32-fallback` implied by `-D warnings`
error: could not compile `rustortion-ui` (lib) due to 3 previous errors

This is toolchain drift, not a code regression. CI uses dtolnay/rust-toolchain@stable, which now resolves to 1.97.0. That release adds the future-incompatible lint float_literal_f32_fallback, which fires on unsuffixed float literals whose type is only settled by inference fallback. Our -D warnings turns it into a hard error.

Fix

Suffix the three affected slider .step() literals as _f32 — exactly what rustc suggests.

• rustortion-ui/src/app.rs — HP and LP cutoff sliders
• rustortion-ui/src/components/ir_cabinet_control.rs — IR gain slider

No behaviour change. These literals already resolved to f32; the suffix just states it explicitly instead of leaning on fallback.

Verification

The lint doesn't exist on older toolchains, so a local make lint on 1.95 passes even without this fix — it can't prove anything. Verified against 1.97 specifically, matching CI:

$ rustc +1.97 -W help | grep float-literal
  float-literal-f32-fallback  warn  detects unsuffixed floating point literals whose type fallback to `f32`

$ cargo +1.97 clippy --workspace --all-targets --all-features -- \
    -D warnings -D clippy::all -D clippy::pedantic -D clippy::nursery
    Finished `dev` profile [optimized + debuginfo] target(s) in 16.86s

$ cargo +1.97 fmt --all -- --check
(clean)

Note on #264

#264 needs this on main and then a rebase — its own diff is unrelated. Once this lands, dependabot will rebase and its Lint job should go green.

[Copilot]

Pull request overview

This PR fixes CI lint failures introduced by Rust toolchain drift (stable → 1.97), where -D float-literal-f32-fallback turns unsuffixed float literals in slider .step() calls into hard errors. It resolves the issue by explicitly suffixing the affected .step() literals with _f32, matching rustc’s suggestion and preserving behavior.

Changes:

• Add _f32 suffix to the HP cutoff slider step literal in SharedApp::view_io_tab.
• Add _f32 suffix to the LP cutoff slider step literal in SharedApp::view_io_tab.
• Add _f32 suffix to the IR gain slider step literal in IrCabinetControl.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
rustortion-ui/src/app.rs	Suffixes the HP/LP cutoff slider .step() literals with _f32 to satisfy the new lint on Rust 1.97.
rustortion-ui/src/components/ir_cabinet_control.rs	Suffixes the IR gain slider .step() literal with _f32 to satisfy the new lint on Rust 1.97.

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