feat(ui): expose use_xxx() factory API for 8 hook primitives and add 4 example pages

[eastspire]

Summary

Wire the eight previously headless euv-ui hook primitives to actual public API surfaces (use_xxx() factories + Copy + R2.1 ///) and add four demonstration pages (hooks-timing / hooks-async / hooks-protect / hooks-i18n) so the example project consumes them end-to-end. Bump the workspace to 0.17.0 (minor) since this PR adds new public functions to the euv-ui crate.

Part 2 of the user's "complete the missing components and hooks" series — Part 1 (PR #39) already added the missing /// summaries on R2.1-critical impl blocks; this PR finishes the job by exposing the factory functions the doc-comments already advertise.

What landed

A. euv-ui hook-layer public API surface

Hook	New factory	Visibility bump	Doc comment added
use_debounced_value::<T>(delay_ms: u32)	pub fn in hook/debounced_value/fn.rs	DebouncedValue<T>: Copy (impl)	/// on the new impl block
use_throttled_value::<T>(interval_ms: u32)	pub fn in hook/throttled_value/fn.rs	ThrottledValue<T>: Copy (impl)	/// on the new impl block
use_previous::<T>() + previous_step(...)	pub fn in hook/previous/fn.rs	Previous<T>: Copy (impl)	/// on the new impl block
use_lazy_component::<T, F>(factory: F)	pub fn in hook/lazy/fn.rs	(already Clone)	/// on the new impl block
use_suspense::<T>()	pub fn in hook/suspense/fn.rs	SuspenseHandle<T>: Copy (impl)	/// on the new impl block
use_error_boundary()	pub fn in hook/error_boundary/fn.rs (extracted from the helper that the existing impl block needs)	ErrorBoundary: Copy (impl)	/// on the new impl block
use_profiler() + profiler_measure(label, body)	pub fn in hook/profiler/fn.rs (with the now_ms pub fn js-sys wrapper that the impl already expected)	ProfilerHandle: Copy (impl)	/// on the new impl block
use_i18n(init_locale) + i18n_register(handle, locale, &[(&'static str, &'static str)]) + interpolate(template, vars) (the existing impl needed but was never defined)	pub fn + pub(crate) fn in hook/i18n/fn.rs	I18n: Copy (impl)	/// on the new impl block
use_async::<T, L>() (uses the existing UseAsyncHandle::new_for_fallback path; HookContext::use_async is on the roadmap but does not exist in euv-core yet)	pub fn in hook/use_async/fn.rs	UseAsyncHandle<T, L>: Copy (impl)	/// on the new impl block

Plus:

• ProfilerHandle::new_with_empty_entries() — hand-written because Lombok New cannot synthesise the default Signal<...> field.
• #[get(type(copy))] on DebouncedValue::value and ThrottledValue::value so the call site can read the emitted value through a Copy boundary instead of borrowing.
• All eight mod.rs files updated to the rust-standards three-section shape: mod r#fn; (where applicable) + pub use {r#fn::*, ...} + trailing use super::*;.
• error_boundary/mod.rs re-exports extract_message and use_error_boundary at the visibility the rest of the crate expects.

B. Example demo pages (4 new pages, 29 → 33)

Each page lives in example/src/page/hooks_{timing,async,protect,i18n}/, with mod.rs + hook/{fn,mod}.rs + view/{fn,struct,mod}.rs mirroring the existing page template (per euv-ui-standards §8).

Route	Consumes	Demo
/hooks-timing	use_debounced_value + use_throttled_value + use_previous	Live input debounce / throttle parallel display, plus a "previous-render snapshot" row
/hooks-async	use_async + use_lazy_component + use_suspense	AsyncState toggle / lazy load / suspend-resolve-fail-reset trio
/hooks-protect	use_error_boundary + use_profiler	Panic capture / measurement log
/hooks-i18n	use_i18n	English / Chinese locale switch with the same two keys

view/fn.rs correctly applies the R2.1 /// doc-comment contract on every fn and impl block.

C. Navigation + routing registration

example/src/component/nav/view/const.rs gets four new NAV_ITEMS rows; example/src/component/router/view/fn.rs gets four new match arms; example/src/page/mod.rs adds the four new modules and exports.

Verification

cargo check -p euv-ui
cargo check -p euv-example
cargo check -p euv-example --target wasm32-unknown-unknown
euv fmt

The audit_rust_standards 14-item suite remains 100% green; the targeted R2.1 scan (fn + impl regex + "block immediately above has ///") reports Missing fn /// = 0, Missing impl /// = 0 across ui/src after this change.

Versioning

Workspace bumps from 0.16.1 to 0.17.0 (minor). New pub functions are added but no existing signature changes / breaks — patch bump would technically suffice, but the 0.16.x series was the "docs compliance + new example pages" rollout; 0.17.0 matches the new pub-surface.

Per project memory: CI's sync_workspace_version job propagates the root bump, publish job pushes the crate to crates.io, release job cuts the git tag + GitHub Release. No manual intervention needed on those steps once the PR merges into master.

Scope / non-goals

• HookContext::use_*() methods are not added — that lives in euv-core, which this PR deliberately leaves untouched.
• App::use_*() wrappers in euv-core are not added — same reason.
• The form, transition, i18n HookContextExt impls remain exactly as upstream ships them. New use_xxx factories in euv-ui are the public-API alternative that already works today.
• No Cargo.toml formatting change other than the version bumps. taplo fmt was not run (no rule requires it for a Cargo.toml lines-only edit).

Followup (out of scope)

• HookContext::use_async(T, L, factory) is the natural next step — it would replace the new_for_fallback() path that use_async currently relies on. That requires an euv-core change.
• HookContext::use_form, use_i18n, use_transition already exist but currently route through their HookContextXxxExt traits; the new use_xxx factories in euv-ui are independent and additive.