Repair the docs build, and bring the quickstart to 2.0.0

[Rafael-SOWNet]

Merge this after v2.0.0 is published on NuGet — the quickstart tells the reader to
install a version that has to exist first. Everything else here is a repair and is
independent of that.

The docs build has been broken since 2026-01-03

asc-community/AngouriMath@f0db3eef moved the library up a folder, and two places here still
pointed at the old layout:

	was	is
amsite.fsx publish	src/AngouriMath/Sources/AngouriMath/AngouriMath	.../Sources/AngouriMath
NaiveStaticGenerator reading AngouriMath.xml	the same stale path	the same fix

The first made dotnet fsi amsite.fsx init fail outright, so nothing downstream ran. The
second would have produced an empty almanac even if the publish had succeeded. They have to
move together and each now says so in a comment.

Two further things stopped it independently, so fixing only the paths would not have been
enough:

• NaiveStaticGenerator targeted net6.0, out of support since November 2024 and not
  present on a current machine — dotnet fsi amsite.fsx build fails with
  "To install missing framework… 6.0.0". Now net10.0. Yadg.NET stays on net6.0 and is
  referenced as a library, which is fine.
• The workflows used actions/checkout@v2 and actions/setup-dotnet@v1, which GitHub no
  longer runs. Now @v4, one setup-dotnet at 10.x instead of separate .NET 6 and .NET 7
  steps, and github-pages-deploy-action@v4 instead of a pinned 4.1.4. The nine ls lines
  that debugged the old paths are gone, and the deployment job declares
  permissions: contents: write for the gh-pages push.

Verified end to end on this commit: init then build produces 1944 pages. The almanac
is among them and reflects 2.0 — docs/AngouriMath/Entity/Latexize.html is there, Ceil,
Floor, Round, Min, Max and Gcd are there, and the members 2.0 removed are not.

Quickstart

• --prerelease is gone. It was installing 2.0.0-preview.2 against pages describing
  something else.
• The MyGet nightly instructions are gone. The feed URL answers but lists no AngouriMath
  package, and it was retired in asc-community/AngouriMath#701. Same for the #i form in
  the notebook section.
• The F# and notebook hello-world programs did not compile. They opened Core and
  Functions by paths that do not resolve, and called parse and differentiate, which are
  parsed and derivative. This was the first program a new F# reader runs.
• The C++ snippet had a stray ; after its #include and no <iostream>.
• Added which frameworks the package targets, because a net7.0 project now resolves the
  netstandard2.0 asset and loses the generic-math surface with it, and a pointer to
  BREAKING-CHANGES.md for anyone coming from 1.x.

The C# and F# hello-world blocks now carry <!-- amcheck:cs --> / <!-- amcheck:fs -->, so a
harness compiles and runs them against a build of the library. Both pass. The annotation is
an HTML comment and does not render. 28 other pre code blocks on the site are shell, CMake
or notebook lines and are not annotated; that count is reported rather than passed over.

What's new

PackageReleaseNotes in every published package sends the reader to /whatsnew, whose
newest entry was 1.4-preview.4, marked "in development". Added the 2.0.0 entry: the
renames and removals, the answers that changed because the old ones were wrong, what is new,
and a link to BREAKING-CHANGES.md at the top, since several entries are a wrong answer
becoming a right one and that still breaks code built on the wrong one. 1.4-preview.4 loses
its "[in development]".

Also

README.md said to install .NET 6 to run the site locally; it is .NET 10 now.

Related: asc-community/AngouriMath#883 is the release itself, and the wiki has been
corrected and is now machine-checked against a 2.0.0 build (86 samples, 0 compile errors, 0
output mismatches).