feat: drop heuropt-plot companion crate

Removes the heuropt-plot subcrate, the visualize example that used
it, and the related workspace plumbing (root [workspace] table, the
[workspace] override added to fuzz/Cargo.toml to detach from it,
heuropt-plot dev-dep, CHANGELOG mention).

The visualization concern is better served as an independent third-
party project than as a companion crate in this repo. No effect on
heuropt's public API or the async work in 0.8.0.

CHANGELOG.md

@@ -7,19 +7,6 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
-### Added
-
-- **`heuropt-plot` companion crate (v0.1.0)** at `heuropt-plot/`,
-  published independently. Lightweight SVG-only plotter for Pareto
-  fronts (`pareto_front_svg`) and convergence traces
-  (`convergence_svg`) — hand-rolled SVG output, no `plotters` /
-  `tiny-skia` dep so the crate stays a tiny optional addition.
-- `examples/visualize.rs` — runs NSGA-II on Schaffer N.1 and writes
-  `pareto_front.svg` via the new `pareto_front_svg` helper.
-- Workspace setup at the repo root: `[workspace] members = [".",
-  "heuropt-plot"]` so both crates share a target dir and one
-  `cargo` invocation builds the lot.
-
 ## [0.8.0] — 2026-05-06
 
 Theme: async evaluation. heuropt now supports problems where each