Repair embedded dependency build and test setup

Isolate vendored test registration, namespace project error codes, and update dependency revisions. Fix mutable sprite path handling, out-of-tree fixtures, and charviewer initialization while documenting the outstanding character-to-sprite refcount bug.

Co-authored-by: Codex (GPT-5) <noreply@openai.com>

AGENTS.md

@@ -0,0 +1,44 @@
+# Repository Guidelines
+
+## Project Structure & Module Organization
+
+This is a C library intended to support the development of video games. Public C headers live in `include/akgl/`; keep declarations there aligned with their implementations in `src/`. Tests are standalone C programs under `tests/`, with JSON, image, and map fixtures in `tests/assets/`. The `util/` directory contains the `charviewer` utility and its sample assets. Third-party and companion libraries are vendored in `deps/`. Treat `build/`, generated `akgl.pc` files, and `include/akgl/SDL_GameControllerDB.h` as build outputs rather than hand-maintained source.
+
+## Build, Test, and Development Commands
+
+Configure an out-of-tree development build:
+
+```sh
+cmake -S . -B build -DCMAKE_BUILD_TYPE=RelWithDebInfo
+```
+
+Build all library, utility, and test targets:
+
+```sh
+cmake --build build --parallel
+```
+
+Run the complete test suite with failure details:
+
+```sh
+ctest --test-dir build --output-on-failure
+```
+
+Run one test while iterating, for example `ctest --test-dir build -R sprite --output-on-failure`. The `rebuild.sh` script also installs into a developer-specific `/home/andrew/local` prefix and removes existing outputs; prefer the portable commands above unless that exact workflow is intended.
+
+## Coding Style & Naming Conventions
+
+Follow the surrounding C style: braces on the next line for function bodies, spaces inside control-flow parentheses, and short, focused functions. Preserve the indentation of the file being edited; older files contain both spaces and tabs. Public symbols use the `akgl_` prefix, public types use `akgl_TypeName`, and constants/macros use `AKGL_UPPER_SNAKE_CASE`. Name matching header/source pairs by feature, such as `include/akgl/sprite.h` and `src/sprite.c`. No repository-wide formatter or linter is configured, so avoid unrelated formatting churn.
+
+## Rules
+
+- Add yourself (agent program name, model name and version) as a co-author on every commit message
+- Avoid dynamic memory allocation. Use the `akgl_heap_*` methods to retrieve necessary objects at runtime, and to release them when done. If the akgl heap facilities don't provide the kind of object needed, create a new heap layer to support that type of object.
+
+## Testing Guidelines
+
+Tests use simple executable return codes and are registered through CTest in `CMakeLists.txt`; there is no declared coverage threshold. Add focused tests as `tests/<feature>.c`, create a matching `test_<feature>` target, and register it with `add_test`. Put reusable fixtures in `tests/assets/` and keep paths compatible with tests launched from the build tree.
+
+## Commit & Pull Request Guidelines
+
+Recent commits use concise, imperative summaries such as `Fix a scale bug...` and often explain related changes in one sentence. Keep each commit scoped and describe user-visible behavior. Pull requests should summarize the change, identify affected modules, list the CMake/CTest commands run, and link relevant issues. Include screenshots only for rendering, map, or `charviewer` changes.