Move Sidenav keyboard shortcut into Leptos

[JamesbbBriz]

Problem

The Sidenav keyboard shortcut was owned by a globally loaded JavaScript sidecar. That bypassed the Leptos component lifecycle, queried the DOM globally, and required the application shell to load component-specific JavaScript.

What changed

• move Ctrl+B / Cmd+B handling into SidenavWrapper
• update the existing RwSignal<bool> through SidenavContext
• ignore input, textarea, and inherited contenteditable focus targets
• reject Shift/Alt-modified shortcuts and respect an already-handled event
• remove the listener explicitly when its wrapper unmounts
• remove the obsolete sidenav.js file and shell script tag
• use Leptos re-exports for browser bindings and close the registry's Cargo dependency metadata
• add browser coverage for normal shortcuts, editable targets, event arbitration, exact modifiers, and unmount/remount cleanup
• synchronize the distributable registry source and update the changelog

Security impact

No network listeners, telemetry, remote state, permissions, or background data transfer were added. The change removes a globally loaded script and scopes the keyboard handler to the mounted component lifecycle.

Verification

PORT=3000 pnpm --dir e2e exec playwright test tests/components/sidenav.spec.ts --project=chromium --workers=1
# 9 passed

CARGO_ENCODED_RUSTFLAGS=$'-C\x1fsymbol-mangling-version=v0\x1f--cfg\x1ferase_components' cargo +nightly-2026-07-23 test -p registry --lib
# 35 passed

CARGO_ENCODED_RUSTFLAGS=$'-C\x1fsymbol-mangling-version=v0\x1f--cfg\x1ferase_components' cargo +nightly-2026-07-23 test --workspace --lib --bins --tests
# 254 passed

cargo +nightly-2026-07-23 test --bin ui
# 310 passed

CARGO_ENCODED_RUSTFLAGS=$'-C\x1fsymbol-mangling-version=v0\x1f--cfg\x1ferase_components' cargo +nightly-2026-07-23 check -p app --no-default-features --features ssr

CARGO_ENCODED_RUSTFLAGS=$'-C\x1fsymbol-mangling-version=v0\x1f--cfg\x1ferase_components' cargo +nightly-2026-07-23 leptos build

cargo +nightly-2026-07-23 fmt --all -- --check
leptosfmt --check app_crates/registry/src/ui/sidenav.rs
git diff --check

A clean standalone consumer fixture containing the distributed Sidenav source also passes cargo check with the dependencies resolved by ui init plus the registry-declared leptos_router and strum/derive dependencies.

The unrestricted cargo test --workspace reaches two pre-existing leptos_ui doctest failures (void references an undefined url, and one variants example omits the macro import). Both failures are outside this change; all workspace library, binary, integration, and unit tests pass.

Fixture and migration notes

• no storage or data migrations
• no production-like fixtures
• registry Cargo metadata now declares the component's existing compile-time dependencies

Closes #28