release: v2.2.4 "Cartridge" — libretro core builds/installs for RetroArch

.github/release-notes/v2.2.4.md

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+# RustyNES v2.2.4 — "Cartridge" (libretro core builds/installs for RetroArch)
+
+A **libretro / RetroArch distribution** cut. Its single purpose is that the RustyNES core **builds and installs cleanly through the Libretro buildbot** ([git.libretro.com/libretro/RustyNES](https://git.libretro.com/libretro/RustyNES)), so RetroArch users can pull it straight from the in-app **Online Updater → Core Downloader**.
+
+A *cartridge* is the thing you slot in to play. That is what this release is about: getting the RustyNES core packaged and advertised correctly so it drops into RetroArch and runs.
+
+**Zero emulation-core changes.** The deterministic `#![no_std]` chip stack, the save-state / TAS / netplay formats, and every golden vector are **byte-identical to v2.2.3**, so **AccuracyCoin holds 141/141 (100.00%)** and nestest is 0-diff *by construction*.
+
+---
+
+## The libretro core is complete, current, and builds for the buildbot
+
+`crates/rustynes-libretro` is a thin wrapper over `rustynes-core`, so it inherits every recent change automatically — it needed no code change to carry the v2.2.3 work:
+
+- **The fast PPU dot path** is the core default now, so the libretro core gets the ~11% rendering-heavy win for free (it constructs `Nes` with the current defaults).
+- **The `PPU_SNAPSHOT_VERSION` 8 / APU v4 save-state schema** is transparent to the wrapper: `get_serialize_size` and `on_serialize` size and emit the *current* snapshot via `Nes::snapshot_core_into` / `VsDualSystem::snapshot`, not a hardcoded layout. RetroArch save states, run-ahead, and rollback netplay therefore carry the v8 sprite-evaluation FSM + OAM data-bus state with no wrapper change — and because libretro save states are session-local, the ADR-0028 epoch never enters the picture.
+- **The `Mapper::mix_audio` i32 widening**, the Zapper model, and the `mNNN_` mapper rename are all below the crate's public dependency surface.
+
+Both buildbot cross-ABIs the GitHub early-warning gate models build clean, verified with the exact CI command:
+
+```text
+cargo check --release -p rustynes-libretro --target x86_64-pc-windows-gnu     Finished
+cargo check --release -p rustynes-libretro --target aarch64-linux-android     Finished
+```
+
+(The full ten-job buildbot recipe went green in v2.2.2; the Apple ABIs are excluded from the Linux-runner gate because bindgen needs a real per-target Apple sysroot.)
+
+## `rustynes_libretro.info` metadata corrected
+
+`rustynes_libretro.info` is the file RetroArch's core downloader reads to learn a core's capabilities. Three entries were stale or wrong:
+
+- **`disk_control` `false` → `true` — the real fix.** The FDS multi-side **Disk Control interface** (`enable_disk_control_interface()` plus the `on_set_eject_state` / `on_get_image_index` / `on_get_num_images` / `on_replace_image_index` callback trampolines) has been wired since the buildbot recipe landed — but the `.info` advertised it as absent, so RetroArch's **Quick Menu → Disk Control** never surfaced multi-disk FDS swapping. Now a Famicom Disk System game with more than one disk side is swappable from the RetroArch UI as intended.
+- **`display_version` `v1.0.0` → `v2.2.4`** — stale since the v1.0.0 era (the runtime `library_version` the core reports has always tracked `CARGO_PKG_VERSION`; this is the static metadata string RetroArch shows).
+- **Description mapper count `168` → `172`**, with a note that FDS multi-disk swapping runs through the Disk Control interface.
+
+## Documented follow-up: libretro core options
+
+Libretro **core options** (region NTSC/PAL/Dendy, overscan crop, palette selection, the opt-in accuracy toggles) remain unexposed. `core_options = "false"` in the `.info` is **accurate, not stale** — the `CoreOptions` impl is deliberately empty. This is a genuine future enhancement, not a v2.2.4 gap: it is a new capability that deserves its own focused work and testing (each option wired to the core config API and verified against the determinism / save-state contract), rather than being rushed into a distribution cut.
+
+## Tooling: the Antigravity reviewer standardized onto the shared template
+
+`scripts/agy-review.sh` and `.github/workflows/antigravity-review.yml` are now byte-identical to the canonical `antigravity-pr-review` template installed across RustyNES / RustySNES / RustyN64, so future reviewer improvements apply uniformly. It carries the large-diff-to-file handling, the 20,000-line `gh pr diff` API-limit local-`git diff` fallback (fetches PR objects but never checks them out), the `isCrossRepository` fork gate, fail-closed metadata, a default-branch checkout with `persist-credentials: false`, and the `synchronize` auto-re-review trigger.
+
+---
+
+## Upgrade notes
+
+- **Nothing breaks.** There are no core, save-state, movie, or netplay changes. `.rns` save states and `.rnm` movies from v2.2.3 load and play identically.
+- **RetroArch users:** once the buildbot mirrors this tag, the RustyNES core appears in **Online Updater → Core Downloader**; FDS multi-disk games gain working Disk Control.
+- No API changes; `Mapper::mix_audio` stays `i32` (unchanged from v2.2.3).
+
+## Verification
+
+```text
+cargo check --release -p rustynes-libretro                          clean
+cargo check --release -p rustynes-libretro --target x86_64-pc-windows-gnu    clean
+cargo check --release -p rustynes-libretro --target aarch64-linux-android    clean
+cargo test --workspace --features test-roms                         AccuracyCoin 141/141, nestest 0-diff
+cargo fmt --all --check · clippy --workspace --all-targets -D warnings · retroachievements combo   clean
+no_std build (thumbv7em-none-eabihf) · markdownlint · actionlint    clean
+```
+
+Mobile versions stay frozen at their v2.0.x host-only release points; the joint store launch remains v2.3.0.