Upgrade wgpu and naga to 30, accesskit to 0.25

[chris-addison]

Stacked on #1 (targets unity/dependency-cleanup).

Changes

• wgpu 29 → 30.0.1, naga 29 → 30.0.1. The API changes, each handled without changing behavior:
  • SurfaceConfiguration.color_space: set to SurfaceColorSpace::Auto, which wgpu documents as its pre-30 behavior (sRGB, or extended linear sRGB for an Rgba16Float surface).
  • RequestAdapterOptions.apply_limit_buckets: set to false. Limit bucketing is an anti-fingerprinting option for code that exposes wgpu to untrusted content, which native gpui doesn't do.
  • SurfaceTexture::present() became Queue::present(frame).
  • hal::metal::Device::texture_from_raw gained a drop callback: None, as before.
  • Device::create_texture_from_hal gained initial_state: TextureUses::UNINITIALIZED, which is what wgpu-core 29 hard-coded for every wrapped texture.
• accesskit 0.24 → 0.25.1, with accesskit_consumer 0.39.1, accesskit_macos 0.27.1, accesskit_unix 0.24.0 and accesskit_windows 0.35.1. Before this, Windows used consumer 0.37 while macOS and Linux used 0.38; now there's one. accesskit::Tree was renamed TreeInfo.
• wgsl-rs validation is no longer on workspace-wide. That feature only backs the #[cfg(test)] validation tests the #[wgsl] macro generates, but it linked wgsl-rs's own naga, still 29 at wgsl-rs's latest commit, into every consumer's normal build. Upgrading gpui to naga 30 would otherwise have left downstream builds with naga 24, 29 and 30.
  • gpui_render, the only crate with #[wgsl] modules, enables it as a dev-dependency, so those 13 generated tests still run.
  • gpui_render's build.rs already validates every pipeline's WGSL with the workspace naga on every build.
  • The one direct wgsl_rs::validate_wgsl_source call, in shaders/tests.rs, now validates with naga 30 directly.

As a result, downstream builds carry only naga 30 plus the deliberate naga-old 24 floor validator. hashbrown 0.15/0.16 and gpu-descriptor also drop out, since wgpu 30 and the new accesskit are on hashbrown 0.17.

objc2 0.5 stays on macOS: even accesskit_macos 0.27.1 still depends on it.

Verification

• macOS: cargo clippy -p gpui-ce -p gpui_ce_platform -p gpui_ce_render -p gpui_ce_wgpu -p gpui_ce_macos -p gpui_ce_apple --all-targets -- -D warnings is clean. cargo test for gpui-ce, gpui_ce_render, gpui_ce_wgpu, gpui_ce_macos and gpui_ce_apple passes, including the headless GPU primitives and the 13 macro-generated WGSL validation tests.
• Windows, cross-checked from macOS: clippy with -D warnings on x86_64-pc-windows-gnu, with screen-capture, is clean. The same redundant_clone at gpui_windows/src/directx_renderer.rs that the base commit already has is allowed on the command line for that run.
• Linux and wasm could not be checked locally, because the Wayland and X11 build scripts need a Linux C toolchain. This PR's CI covers both.
• cargo fmt --all -- --check is clean.

🤖 Generated with Claude Code

[chris-addison]

Landed on unity/a11y-automation by fast-forward to 7b79950, together with #1, so this commit keeps its SHA. Closing, because GitHub can't mark it merged: its base, unity/dependency-cleanup, never received the commit.