Record the real coverage numbers, and how they were nearly misreported

93.5% of lines and 97.8% of functions, up from 92.3% and 96.9% across roughly 800
new lines. The verb groups added for goal 2 carry the new surface: the two table
files and runtime_input.c at 100%, runtime_graphics.c and runtime_audio.c at 98%,
play.c at 87%.

The first reading of that number was wrong and the reason is worth keeping. A
stale build-cov/ left in the source directory by an earlier session was silently
folded in by `gcovr --root .`, which reported the *previous* run's 92.3% for a
tree that had grown by 800 lines -- a number that looked plausible precisely
because it had not moved. That is libakgl defect #13 happening here rather than
there, and build*/ being gitignored is what makes it invisible. Section 8 now
says to check `find . -name '*.gcda'` before believing a coverage figure that
looks suspiciously unchanged.

Also documents the akgl build and test commands in the README, which had none.

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

README.md

@@ -16,6 +16,12 @@ ctest --test-dir build --output-on-failure
 
 # API documentation, into build/docs/html
 doxygen Doxyfile
+
+# With the libakgl-backed sink and devices. Off by default, because this pulls in
+# SDL3 and the whole interpreter builds and tests without it.
+cmake -S . -B build-akgl -DAKBASIC_WITH_AKGL=ON
+cmake --build build-akgl --parallel
+SDL_VIDEODRIVER=dummy SDL_AUDIODRIVER=dummy ctest --test-dir build-akgl --output-on-failure
 ```
 
 There are two workflows. **`.gitea/workflows/ci.yaml`** runs on every push: the suite,

TODO.md

@@ -797,16 +797,30 @@ entire test corpus and passes clean under ASan and UBSan.
 
 | Gate | Result |
 |---|---|
-| `ctest` | 61/61 — 41 golden cases, 17 unit tests, 2 embedding examples, 1 known-failing |
+| `ctest` | 70/70 — 41 upstream golden cases, 5 local ones, 21 unit tests, 2 embedding examples, 1 known-failing |
+| `ctest` with `-DAKBASIC_WITH_AKGL=ON` | 71/71 — the above plus `akgl_backends` |
 | Golden corpus | 41/41 byte-exact, driven in place from the submodule |
-| ASan + UBSan | 61/61 |
+| ASan + UBSan | 70/70 |
-| Line coverage | 92.3% (2823/3058) — above the 90% gate |
+| Line coverage | 93.5% (3631/3884) — above the 90% gate |
-| Function coverage | 96.9% (221/228) |
+| Function coverage | 97.8% (269/275) |
 | Warnings | none under `-Wall -Wextra` |
-| `doxygen Doxyfile` | clean; 114/114 public declarations documented |
+| `doxygen Doxyfile` | clean |
 | Mutation (`src/convert.c`, `src/symtab.c`) | see `.gitea/workflows/ci.yaml` for the current score and gate |
 
-Branch coverage reads 17.3% and is not a target, for the reason `libakgl/TODO.md` and
+Coverage of the verb groups added for goal 2, since they are the new surface: `src/audio_tables.c`
+and `src/graphics_tables.c` 100%, `src/runtime_input.c` 100%, `src/runtime_graphics.c` and
+`src/runtime_audio.c` 98%, `src/play.c` 87%. The `akbasic_akgl` target is not in the coverage
+figure — it is not built in a default configuration.
+
+**A note on reading that number, because it was misread once while producing it.** A stale
+`build-cov/` left in the source directory from an earlier session was silently folded into the
+report by `gcovr --root .`, which produced the *previous* run's 92.3% for a tree that had grown
+by 800 lines. That is `libakgl` defect #13 happening here rather than there, and `build*/` being
+gitignored is exactly what makes it invisible. **Keep build trees out of the source directory**,
+and if a coverage number looks suspiciously unchanged, `find . -name '*.gcda'` before believing
+it.
+
+Branch coverage reads 18.0% and is not a target, for the reason `libakgl/TODO.md` and
 `libakstdlib/TODO.md` both give: the akerror control-flow macros expand into large branch trees
 at every call site, most of them unreachable in normal operation. Track line and function
 coverage.