fix(frontend): add the missing /api/ link to the wasm demo page

[doublegate]

Summary

• The user compared RustySNES's live Pages deployment against RustyNES's and found the demo page has no path to the API docs — RustyNES's root page has <a href="api/">API documentation</a> in a small footer; RustySNES's had nothing (you'd have to manually type /api/ into the URL bar).
• Adds a matching footer (<p class="hint">) with a GitHub repo link + an API docs link, styled to match the existing dark theme.
• Verified locally: RUSTFLAGS="-C target-feature=-reference-types" trunk build --release --public-url /RustySNES/ produces the footer correctly in dist/index.html.

Separately investigated, not part of this PR: the user also reported the demo canvas itself renders blank. Root-caused via a headless-Chromium (Playwright) load with full console/network capture: the wasm module loads and initializes without any errors (window.wasmBindings populates correctly), but crates/rustysnes-frontend/src/wasm.rs is — and has always been — an explicitly-labeled scaffold stub ("v0.1.0: a minimal bootstrap... The full browser frontend... is a TODO for the implementation phase"). It installs a panic hook and logs one console message, then returns — it never builds the App, creates a wgpu surface from a <canvas>, or drives a requestAnimationFrame loop. This isn't a regression from this session's PRs; it predates all of them. Every "wasm demo is live" verification this project has done so far (v0.1.0 onward) checked HTTP-level liveness (200 status, correct content-types) — not that the app actually renders. RustyNES's own wasm frontend spans 13 files (wasm.rs, wasm_winit.rs, wasm_audio.rs, wasm_gamepad.rs, wasm_io.rs, wasm_idb.rs, wasm_save_states.rs, wasm_touch.rs, wasm_lobby.rs, wasm_script.rs, wasm_cheevos.rs, wasm_netplay.rs, wasm_share.rs) for comparison — building RustySNES's out to real parity is genuinely substantial work, not a quick fix, and is being raised separately for scoping/sequencing against the v0.8.0+ ladder rather than folded into this small PR.

Test plan

• Local trunk build --release succeeds, footer present in output
• Markdown integrity check on the CHANGELOG entry

🤖 Generated with Claude Code

[gemini-code-assist]

Code Review

This pull request adds a footer to the WebAssembly demo page with links to the GitHub repository and the API documentation, along with corresponding CSS layout adjustments and a changelog entry. The reviewer suggests opening these links in a new tab using target="_blank" to prevent users from losing their active emulation state when navigating away.

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