Dash iterator zero-length LineTo noise

@waywardmonkeys is already working on this.

Since Jul 23, 2026.

• #578 by @RobertBrewitz — closed without merging
• #597 by @waywardmonkeys — open

If/When https://github.com/linebender/kurbo/pull/550 is merged this would be a follow-up issue.

When a dash transition lands exaxtly on a path vertex, the iterator emits a zero-length `LineTo` at the corner instead of cleanly transitioning to the next dash.

Example:

```rust
let mut path = BezPath::new();
path.move_to((0., 0.));
path.move_to((3., 0.));
path.move_to((3., 3.));
let dashes = [3., 1.];
let result: Vec = dash_iter(path.into_iter(), 0., &dashes, true).collect();

// Current noisy output: MoveTo(0,0), **LineTo(3,0), LineTo(3,0)**, MoveTo(3,1), LineTo(3,3)
// Expected output: MoveTo(0,0), LineTo(3,0), MoveTo(3,1), LineTo(3,3)
```

Start with the `dash_iter` entry point and reproduce the issue using the Rust example in this report. Check the open PR #597 before beginning, then verify that a dash transition at a vertex no longer emits a duplicate zero-length `LineTo` and that the expected path elements are produced.

Written by the indexing model from the issue text.