Merge master into StarForth-v4.0.0: the branch's build, master's CI files kept

For PR #30. master's 9 commits since the fork (T= board selection,
mk/boards.mk, build.yml, the nightly workflows) conflicted in four
files; each is resolved to the branch's version:

  .gitea/workflows/nightly.yml       added on both; master's copy named
  .gitea/workflows/nightly-docs.yml  the branch in its checkout, the
                                     branch's builds the default branch
  Makefile                           master's T= and mk/boards.mk against
  kernel/Makefile                    the branch's TARGET=<board> and
                                     boards/; master's edits were to
                                     Makefile.starkernel, renamed here

The two workflows' header comment now says they build master.

Merged cleanly from master: build.yml (its board matrix, Nexus publish
and 02:00 nightly; it still calls Makefile.starkernel and make
T=<board>, which this tree does not have -- #18) and mk/boards.mk
(nothing here includes it).

Against the branch the merge changes only those CI files and
mk/boards.mk: no kernel, v4 or Makefile source, so the build is the one
accepted on 2026-11-06.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GE3SDvQn5EoxdGufk84zz2

.gitea/workflows/nightly-docs.yml

@@ -6,8 +6,7 @@
 #     classifier vol1, vol2, vol3   the formal volumes (make -C docs/formal vols)
 #     classifier api    the API reference (make -C docs/formal doxygen)
 #
-# Gitea runs a schedule from the default branch. Until StarForth-v4.0.0 is merged to master,
-# master carries a copy of this file whose checkout names that branch.
+# Gitea runs a schedule from the default branch, master, so this builds master.
 name: Nightly documents
 
 on:

.gitea/workflows/nightly.yml

@@ -8,8 +8,7 @@
 #     classifier milkv   MilkV.img.xz     Milk-V Mars
 #     classifier logs    logs.tar.gz      this run's serial logs, proof log and DoE CSVs
 #
-# Gitea runs a schedule from the default branch. Until StarForth-v4.0.0 is merged to master,
-# master carries a copy of this file whose checkout names that branch.
+# Gitea runs a schedule from the default branch, master, so this builds master.
 name: Nightly snapshot
 
 on: