nfty 1.2.7 — the README, rewritten against the code

The README is rewritten. No engine, CLI or GUI behaviour changes in this release — the
binaries are 1.2.6's, rebuilt so every archive carries the new file.

The README

It now follows the flow the other Vaporsoft repos use: tagline, grounded intro, grouped
badges, Table of Contents, Overview and Capabilities, Requirements, Installation, Quick
Start, Concepts, Architecture, Command Line, Desktop Application, Performance,
Development, Deployment, Troubleshooting, Links, Contributing.

Every figure in it was checked against the repository rather than carried over:

• Five real commands were missing — demo, export, add rule, remove rule and
  set chance — and inspect had grown .set and .tin since the table was written.
• The test badge said 1672 and the layout said 1454. A full run is 2,088: 152 CLI,
  1,058 Core, 878 App.
• 615,600 was re-derived with stats, and the demo's eighteen distinct sprites counted
  out of the archive itself.
• Sealing, export, optional layers and the counted DNA space had no place in the file
  at all, which left the two features most likely to be asked about undocumented.
• Two screenshots were drafted and pulled again: docs/manual/images/ still shows Vapor
  Pets on the pre-1.2 card layout, which BACKLOG.md already holds as a deferred reshoot.
  A stale frame in a README is worse than none.

The project tree and the pipeline sketch were also brought under 80 columns, so a narrow
viewport no longer cuts the right-hand end off every line.

Downloads

	Size	.NET 10 needed
Portable	84 MB	no — unzip anywhere and run. Start here if you are unsure.
Single file	76 MB	no — one .exe. Unpacks itself on first run, so that launch is slower.
Single file, .NET	14 MB	yes — one .exe, runtime left out.
Framework-dependent	14 MB	yes — the same, as a folder.

The two .NET builds need the .NET 10 desktop
runtime; the other two carry everything.