feat(qwen38flashnext): add the finished engine

Qwen3.8-Flash-Next's final version after a 14.5-hour optimization run
(its commit 7d7fca3): cost-first sheet trials, largest-area-first
demand order, and a cached-triangulation exact gate that brought a
219-part production job from timeout to ~106 s. 13/13 tests pass
against OpenNest master.

README cleaned for publishing: the model-facing template rules are
replaced by a one-line independence statement, the production job is
described generically instead of by its PEP job/file name (also in a
JobSolver comment), results show both sheet pools as re-measured here
(the 9-size claim in its report didn't reproduce: it grabs 96x240 and
under-fills them), and the stale StockLadder-crash note is gone now
that core leaves etch marks out of nesting.

Also drops a stale Aurora plugin reference from Opus55's README and
lists the engine in the repo README.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

OpenNest.Engine.Qwen38FlashNext/Qwen38FlashNextNestingEngine.cs

@@ -0,0 +1,48 @@
+using System;
+using System.Threading;
+using OpenNest.Engine.Jobs;
+using OpenNest.Engine.Qwen38FlashNext.Engine;
+
+namespace OpenNest.Engine.Qwen38FlashNext;
+
+/// <summary>
+/// Independent whole-job nesting engine: bottom-left-first placement over convex
+/// No-Fit-Polygons with an exact material-clearance gate, driven sheet by sheet by a
+/// greedy demand scheduler.
+/// <para>
+/// Per sheet, parts are demanded in the engine's own order (priority, then the
+/// largest material area, then id) and each requirement is drained greedily. For a part instance the engine enumerates its
+/// legal orientations (policy angles, or 0/90/180/270 plus the rotating-calipers
+/// minimum bounding rectangle for automatic rotation), builds for every placed part a
+/// convex NFP as placedHull (+) disk(spacing) (+) reflect(candidateHull) via its own
+/// Minkowski edge-merge, generates the corner-point feasible-region candidates (anchor
+/// box corners, NFP vertices, NFP-edge/box-line slides), and places the instance at the
+/// lowest-leftmost candidate whose exact material clearance the engine's collision gate
+/// accepts (cached-triangulation clip with a sound fast-shell prefilter). Which stock
+/// the next sheet uses is chosen by re-packing each available size and committing the
+/// trial that delivers the cheapest plate area per unit of part area placed; the
+/// job stops when demand is met, stock runs out, nothing further can be placed, or the
+/// plate cap is hit. See Engine/ for the placement core and README.md for the design
+/// write-up.
+/// </para>
+/// <para>
+/// The engine is self-contained: it calls no built-in <see cref="INestingEngine"/>,
+/// nester, filler, or runner, and is deterministic - identical input, identical layout.
+/// </para>
+/// </summary>
+public sealed class Qwen38FlashNextNestingEngine : INestingEngine
+{
+    public NestJobResult Solve(
+        NestJob job,
+        IProgress<NestJobProgress>? progress = null,
+        CancellationToken token = default
+    )
+    {
+        ArgumentNullException.ThrowIfNull(job);
+        token.ThrowIfCancellationRequested();
+
+        var preparation = new PartPreparation(job.Parts);
+        var solver = new JobSolver(job, preparation);
+        return solver.Solve(progress, token);
+    }
+}