Check the reference corpus in, so the build stops needing the Go submodule

All 41 .bas/.txt pairs copied byte for byte from basicinterpreter@d76162c into
tests/reference/, plus the Commodore font into assets/fonts/ -- the two things
that tied the build to deps/basicinterpret. Both were verified cmp-identical
to the submodule copies.

This reverses a decision that was deliberate and correct at the time: the
corpus was driven in place because copying a submodule's corpus guarantees
drift. Overruled on purpose -- the Go dependency is being deprecated, and a
build that cannot run its acceptance suite without cloning the implementation
it replaced is not finished. tests/reference/README.md records what the drift
now costs and that those expectations are never edited.

Checked rather than assumed: both configurations configure, build and pass
from scratch with deps/basicinterpret moved out of the tree entirely.

The submodule is kept as the behavioural spec, which is a real use. The font
came with an open licence question; assets/fonts/PROVENANCE.md states it.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

.gitea/workflows/ci.yaml

@@ -15,8 +15,10 @@ jobs:
         uses: actions/checkout@v4
         with:
           # Not recursive, deliberately. The top-level build needs
-          # deps/libakerror and deps/libakstdlib (via add_subdirectory) and
-          # deps/basicinterpret (the golden corpus is driven in place from it).
+          # deps/libakerror and deps/libakstdlib, via add_subdirectory, and
+          # nothing else: the golden corpus and the Commodore font now live in
+          # this repository (tests/reference/ and assets/fonts/), so
+          # deps/basicinterpret is no longer a build dependency at all.
           # It does *not* need deps/libakgl, which is guarded behind
           # AKBASIC_WITH_AKGL and defaults OFF -- and recursing into it would
           # clone SDL, SDL_image, SDL_mixer, SDL_ttf and jansson for a target
@@ -32,12 +34,13 @@ jobs:
         run: |
           cmake -S . -B build
           cmake --build build --parallel
-      # The suite is 70 cases: 41 golden files byte-compared against the Go
-      # reference's own corpus, 5 local golden cases for verbs the reference
-      # never implemented, 21 unit tests, 2 embedding examples, and 1
-      # known-failing test that asserts the *correct* contract for defects
-      # carried over from the reference (TODO.md section 6). A green run
-      # therefore does not mean defect-free -- see AKBASIC_KNOWN_FAILING_TESTS.
+      # The suite is 78 cases: 41 golden files byte-compared against the Go
+      # reference's own corpus (checked in at tests/reference/, see its README),
+      # 9 local golden cases for verbs the reference never implemented, 25 unit
+      # tests, 2 embedding examples, and 1 known-failing test that asserts the
+      # *correct* contract for defects carried over from the reference (TODO.md
+      # section 6). A green run therefore does not mean defect-free -- see
+      # AKBASIC_KNOWN_FAILING_TESTS.
       #
       # AKBASIC_WITH_AKGL is off here, which is the point rather than an
       # omission: this job is what proves the interpreter builds and passes on a
@@ -96,13 +99,14 @@ jobs:
         run: |
           sudo apt-get update -y
           sudo apt-get install -y cmake gcc gcovr
-      # The gate is a ratchet, not a target: src/ sits at 93.5% of lines and
-      # 97.8% of functions, so 90 fails on a real regression (a test deleted, or
+      # The gate is a ratchet, not a target: src/ sits at 94.6% of lines and
+      # 98.6% of functions, so 90 fails on a real regression (a test deleted, or
       # new untested code added) without tripping over rounding.
       #
-      # The akbasic_akgl target is not in this figure. It is not built in a
-      # default configuration, and instrumenting it would drag SDL into the
-      # coverage job for four thin adaptors.
+      # The akbasic_akgl and akbasic_frontend targets are not in this figure.
+      # Neither is built in a default configuration, and instrumenting them would
+      # drag SDL into the coverage job for four thin adaptors and a host. What
+      # covers them instead is the akgl_build job below.
       #
       # There is deliberately no branch gate. Branch coverage reads about 18%
       # and is not a meaningful number here, for the reason libakgl's and
@@ -235,9 +239,9 @@ jobs:
         uses: actions/checkout@v4
         with:
           # The harness copies the repo and configures a build inside the copy,
-          # so it needs the same submodules the main build does -- including
-          # deps/basicinterpret, because the golden corpus is part of what kills
-          # mutants.
+          # so it needs the same submodules the main build does. The golden
+          # corpus is part of what kills mutants and it is checked in now, so
+          # that is libakerror and libakstdlib and nothing else.
           submodules: true
       - name: dependencies
         run: |