docs: remove the 1.96 split everywhere it was still stated as current

3175827 moved the libretro buildbot to Rust 1.99 and gave every crate the
workspace floor. It left the split described as current in places the first
sweep missed (`git grep 1.96`, not run then). Copilot (#590, #591, #593),
CodeRabbit (#591) and agy (#590, #591, #593) each reported subsets.

Fixed:
- the seven libretro-path Cargo.toml files: the "builds this crate on Rust
  1.96.0" comment is deleted, since the inherited workspace value is the fact;
- .cargo/config.toml (the MSRV-aware resolver note);
- ARCHITECTURE.md's tree line;
- CONTRIBUTING.md's MSRV bullet;
- docs/build-and-tooling.md;
- docs/dev/BUILD.md, whose RUSTUP_TOOLCHAIN=1.96.0 command would now be
  rejected by cargo;
- docs/dev/STYLE_GUIDE.md;
- docs/benchmarks.md;
- the webOS comment in .gitlab-ci.yml, plus a header on its #91899
  post-mortem saying which two details have moved since (the pin value, and
  `rustup toolchain install ... --target` in place of `rustup target add`;
  Copilot on #592);
- the bus.rs reborrow comment. The `&mut *self.ram` reborrow is KEPT:
  iterating `&mut Box<[T; N]>` needs 1.97+, both forms compile on the 1.99
  floor, and changing working code buys nothing (agy suggested removing it).

Kept: every 1.96 reference that is dated history (CHANGELOG entries, the
2026-07-20 buildbot post-mortem, rust-toolchain.toml's account of the split,
the plans). A second `git grep -E "1\.96"` after this change shows only those.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014qfTKi2M3swo7qnwvYCkDj

Author: doublegate

.cargo/config.toml

@@ -22,8 +22,8 @@
 rustflags = ["--cfg=web_sys_unstable_apis", "--cfg=getrandom_backend=\"wasm_js\""]
 
 # MSRV-aware (v1.3.0 bumped 1.86 -> 1.96, v3.0.1 -> 1.99) dependency resolution.
-# The workspace pins rust-version = "1.99" and the seven libretro-path crates
-# "1.96"; `fallback` makes `cargo update` prefer dependency
+# Every crate inherits the workspace's rust-version = "1.99" (seven libretro-path
+# crates declared "1.96" for one day in v3.0.1); `fallback` makes `cargo update` prefer dependency
 # versions compatible with that MSRV over the newest available. Without it, a
 # future `cargo update` could pull a past-MSRV crate (e.g. `image` >= 0.26, a
 # transitive dep of `arboard`'s clipboard image support, which needs a newer

.gitlab-ci.yml

@@ -30,12 +30,18 @@
 # ---------------------------------------------------------------------------
 # Why every job carries a `before_script` (pipeline #91899 post-mortem)
 # ---------------------------------------------------------------------------
+# (History, 2026-07-20. The mechanism still holds; two details moved since:
+# the pin is whatever `rust-toolchain.toml` says (1.99.0 at v3.0.1), and since
+# v3.0.1 each job runs `rustup toolchain install ${RUSTUP_TOOLCHAIN} --profile
+# minimal --target ${RUST_TARGET}`, which installs the pinned toolchain WITH
+# its target in one step, where this record says `rustup target add`.)
+#
 # The first buildbot run passed only `libretro-build-linux-x64`; the other
 # nine died with `E0463: can't find crate for core`. Root cause is entirely
 # on our side, not the build images:
 #
-# This repo pins its toolchain in `rust-toolchain.toml` (`channel =
-# "1.96.0"`). The build image ships its own default toolchain with every
+# This repo pinned its toolchain in `rust-toolchain.toml` (`channel =
+# "1.96.0"` then). The build image ships its own default toolchain with every
 # libretro cross target pre-provisioned — but our pin makes rustup download
 # and install a SEPARATE, pristine 1.96.0 toolchain on the first `cargo`
 # invocation, and that toolchain carries only the host `rust-std` plus the
@@ -360,8 +366,8 @@ libretro-build-tvos-arm64:
 # Built in libretro's webOS image, which has its own rustup, libclang and the
 # LG webOS SDKs. The template's `before_script` sources the SDK environment,
 # so it is kept via `!reference`, and the #91899 `rustup target add` follows
-# it: the `channel` pin makes rustup fetch a pristine 1.96.0 here too, without
-# the targets the image installed on its own default toolchain.
+# it: the pinned toolchain (`RUSTUP_TOOLCHAIN`) is a pristine install here too,
+# without the targets the image installed on its own default toolchain.
 libretro-build-webos-armv7a:
   extends:
     - .libretro-rust-webos-armv7a-default

ARCHITECTURE.md

@@ -1,7 +1,7 @@
 # RustyNES Architecture
 
 **Document Version:** 2.1.0
-**Last Updated:** 2026-08-30
+**Last Updated:** 2026-10-07
 **Applies to:** RustyNES v3.0.1 (the scheduling model is v2.0.0 "Timebase" onward)
 
 This document fixes the high-level architecture of RustyNES. The per-subsystem specs under `docs/` (`cpu-6502.md`, `ppu-2c02.md`, `apu-2a03.md`, `mappers.md`, `scheduler.md`) take these decisions as given and elaborate one chip each. After reading this you should know the workspace shape, the scheduling model, the public boundary, and the load-bearing invariants. The canonical, always-current architecture spec is [`docs/architecture.md`](docs/architecture.md); this file is the top-level companion.
@@ -53,7 +53,7 @@ These cross-cutting choices span many files and are not negotiable without re-de
 
 ```text
 rustynes/
-├── Cargo.toml                  # Workspace definition (edition 2024, MSRV 1.99; libretro path 1.96)
+├── Cargo.toml                  # Workspace definition (edition 2024, MSRV 1.99 for every crate)
 ├── crates/
 │   ├── rustynes-core/          # Glue: Nes struct, run loop, scheduler, Bus,
 │   │                           #   save state, region config. Re-exports chip crates.

CONTRIBUTING.md

@@ -134,7 +134,7 @@ forbids, so a flaky test is a bug to fix, not to retry.
 
 - **Format:** `cargo fmt` (rustfmt defaults).
 - **Lint:** pass `cargo clippy --workspace --all-targets -- -D warnings` with no warnings.
-- **Edition:** Rust 2024. **Toolchain:** 1.99 (pinned in `rust-toolchain.toml`). **MSRV:** 1.99, except the seven crates the libretro core builds (`rustynes-{cpu,ppu,apu,mappers,core,gamedb,libretro}`), which keep 1.96 for the libretro buildbot; CI checks them on 1.96.
+- **Edition:** Rust 2024. **Toolchain:** 1.99 (pinned in `rust-toolchain.toml`). **MSRV:** 1.99 for every crate. The libretro buildbot uses the same toolchain (`RUSTUP_TOOLCHAIN` in `.gitlab-ci.yml`), and CI fails if the two ever differ, so move both in one change.
 - The chip stack (`rustynes-{cpu,ppu,apu,mappers,core}`) is `#![no_std]` + `extern crate alloc;`. `unsafe` is only permitted at FFI boundaries (`rustynes-cheevos`) and the one native priority hook in `rustynes-frontend`, and **must** carry a `// SAFETY:` comment explaining the invariant.
 - No emojis in code, comments, or commits (project policy).
 

crates/rustynes-apu/Cargo.toml

@@ -3,7 +3,6 @@ name = "rustynes-apu"
 description = "Cycle-accurate Ricoh 2A03 APU (Audio Processing Unit) for the NES"
 version.workspace = true
 edition.workspace = true
-# The libretro buildbot builds this crate on Rust 1.96.0 (`.gitlab-ci.yml`).
 rust-version.workspace = true
 license.workspace = true
 authors.workspace = true

crates/rustynes-core/Cargo.toml

@@ -3,7 +3,6 @@ name = "rustynes-core"
 description = "Cycle-accurate NES emulator core: scheduler, bus, save state, public Nes facade"
 version.workspace = true
 edition.workspace = true
-# The libretro buildbot builds this crate on Rust 1.96.0 (`.gitlab-ci.yml`).
 rust-version.workspace = true
 license.workspace = true
 authors.workspace = true

crates/rustynes-core/src/bus.rs

@@ -1260,9 +1260,10 @@ impl SystemBus {
             // Byte 3 (bits 24-31) — extracted without a truncating cast.
             s.to_le_bytes()[3]
         };
-        // `&mut *self.ram`, not `&mut self.ram`: `&mut Box<[T; N]>` only
-        // became iterable after Rust 1.96, and this crate builds on 1.96 for
-        // the libretro buildbot. Reborrowing the array works on both.
+        // `&mut *self.ram` reborrows the array: iterating `&mut Box<[T; N]>`
+        // directly needs Rust 1.97+. The crate's floor is 1.99, so either form
+        // compiles today; the reborrow dates from v3.0.1's one-day split, when
+        // the libretro buildbot briefly built this crate on 1.96.
         for byte in &mut *self.ram {
             *byte = next();
         }

crates/rustynes-cpu/Cargo.toml

@@ -3,7 +3,6 @@ name = "rustynes-cpu"
 description = "Cycle-accurate Ricoh 2A03 (6502 derivative) CPU core for the NES"
 version.workspace = true
 edition.workspace = true
-# The libretro buildbot builds this crate on Rust 1.96.0 (`.gitlab-ci.yml`).
 rust-version.workspace = true
 license.workspace = true
 authors.workspace = true

crates/rustynes-gamedb/Cargo.toml

@@ -11,7 +11,6 @@
 name = "rustynes-gamedb"
 version.workspace = true
 edition.workspace = true
-# The libretro buildbot builds this crate on Rust 1.96.0 (`.gitlab-ci.yml`).
 rust-version.workspace = true
 license.workspace = true
 authors.workspace = true

crates/rustynes-libretro/Cargo.toml

@@ -3,7 +3,6 @@ name = "rustynes-libretro"
 description = "Cycle-accurate NES emulator libretro core wrapper"
 version.workspace = true
 edition.workspace = true
-# The libretro buildbot builds this crate on Rust 1.96.0 (`.gitlab-ci.yml`).
 rust-version.workspace = true
 license.workspace = true
 authors.workspace = true