fix(client): honor scroll-margin-top when scrolling to hash

[Mister-Hope]

Summary

Hash navigation ignores scroll-margin-top, so themes cannot keep anchor targets clear of a fixed navbar with it.

The router scrolls with { el: to.hash }, and vue-router resolves that element itself (elRect.top - docRect.top + window.scrollTo) instead of using scrollIntoView, so scroll-margin-top / scroll-padding-top have no effect. Themes are left with a negative margin-top paired with a matching padding-top, which shifts the box (including its padding) above the element and makes the content above it unclickable.

Changes

• packages/client: scroll hash targets with scrollIntoView and return false, so scroll-margin-top is honored.
  • The scroll is deferred to the next frame, which also fixes hash links pointing to another page: the target element has not been rendered yet when the scroll behavior is called, so those links never scrolled at all.
  • getElementById is used instead of querySelector, as an id may contain characters that are invalid in a CSS selector (e.g. the space in #foo bar or the : in #foo:1).

Tests

Added e2e/tests/router/scroll-to-hash.spec.ts with two pages whose targets have scroll-margin-top: 100px, covering:

• a hash on the same page,
• a hash containing special characters (#target:1),
• a hash on another page,
• a hash on another page reached by a markdown link,
• navigating to another page without a hash (still scrolls to the top).

All 5 fail without the change (the target ends up at the top of the viewport, or the page does not scroll at all) and pass with it.

Verification

• pnpm lint, pnpm check-types, pnpm test:unit (666 tests) pass.
• pnpm e2e:dev (86 tests) and pnpm e2e:build (93 tests) pass.

[coveralls]

Coverage Report for CI Build 36333404826

Coverage remained the same at 73.948%

Details

• Coverage remained the same as the base build.
• Patch coverage: No coverable lines changed in this PR.
• No coverage regressions found.

Uncovered Changes

No uncovered changes found.

Coverage Regressions

No coverage regressions found.

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Coverage Stats

Relevant Lines:	1087
Covered Lines:	800
Line Coverage:	73.6%
Relevant Branches:	552
Covered Branches:	412
Branch Coverage:	74.64%
Branches in Coverage %:	Yes
Coverage Strength:	48.34 hits per line

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💛 - Coveralls