fix(examples): register critical-section impl for canvas_waves wasm build

[patrick-andrew-anchor]

Problem

examples/canvas_waves fails to build for wasm32-unknown-unknown (and thus the GitHub Pages deploy fails at the Build examples step):

rust-lld: error: ...libratatui_core-*.rlib(...): undefined symbol: _critical_section_1_0_acquire
rust-lld: error: ...libratatui_core-*.rlib(...): undefined symbol: _critical_section_1_0_release

The example has no committed lockfile, so a fresh resolve pulls a current ratatui_core (via ratzilla/tachyonfx) that depends on critical-section. On wasm32-unknown-unknown nothing registers a critical-section implementation, so the linker can't resolve the acquire/release symbols.

Fix

Add critical-section with the std feature to canvas_waves, which registers the implementation:

critical-section = { version = "1.1", features = ["std"] }

After this, cargo build --release --target wasm32-unknown-unknown (and trunk build) link cleanly.

Notes

• This is pre-existing dependency drift, independent of any feature work — reproducible on a fresh checkout + build of main.
• Single-file change to the example's Cargo.toml; no library code touched.

[orhun]

thx!

would you be possibly interested in fixing this for the other examples too? (if they are a problem there)

[patrick-andrew-anchor]

thx!

would you be possibly interested in fixing this for the other examples too? (if they are a problem there)

I can see if it's an issue, I got CI passing on my fork so 🤷‍♂️

[patrick-andrew-anchor]

Checked the other examples — none need the same treatment, so this stays scoped to canvas_waves:

Example	Target	Pulls ratatui/tachyonfx/ratzilla?
canvas_waves	wasm (trunk)	yes → ratatui_core → critical-section
game-console	native (glutin + winit)	no
terminal-emulator	native (glutin + winit + vt100/portable-pty)	no
native-terminal	native (glutin + winit)	no

game-console, terminal-emulator, and native-terminal are native OpenGL apps — they build for the host target, not wasm32-unknown-unknown, and don't depend on ratatui/critical-section. The undefined _critical_section_1_0_acquire symbol only arises on wasm32 (single-threaded, no registered critical-section impl), so native targets are unaffected. canvas_waves is the only Rust example that builds to wasm and pulls ratatui_core (via ratzilla/tachyonfx), so it's the only one that needs the critical-section/std impl.