Fix timeline nav scroll-to-top on current timeline

[lkjsxc]

Summary

• Reuse the existing Timeline scroll-to-top behavior when the current timeline nav item is clicked again.
• Support same-route clicks for Home and Public timelines.
• Target scroll-to-top requests by timeline route so unrelated mounted timelines do not respond.
• Keep normal navigation for other routes and modified clicks.

Test plan

• npm run lint
• npm test
• npm run check (fails on existing unrelated diagnostics in Restriction.ts, Gdpr.svelte, and channels/[nevent=note]/+page.svelte)

[Copilot]

Pull request overview

This PR updates the app header’s Home/Public navigation so that clicking the currently-active timeline link triggers the existing Timeline “scroll to top” behavior (instead of re-navigating), while keeping normal navigation behavior for other routes and modified clicks.

Changes:

• Add a route-targeted scroll-to-top request mechanism via a window CustomEvent.
• Intercept same-route clicks on Home/Public header links to dispatch a targeted scroll-to-top request.
• Wire Timeline instances on /home and /public to listen for scroll-to-top requests for their own route only.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
web/src/routes/(app)/public/+page.svelte	Passes scrollToTopTarget="/public" to the public timeline so it can respond only to relevant scroll-to-top requests.
web/src/routes/(app)/home/+page.svelte	Passes scrollToTopTarget="/home" to the home timeline so it can respond only to relevant scroll-to-top requests.
web/src/routes/(app)/Header.svelte	Adds same-route click handling for Home/Public to dispatch a targeted scroll-to-top request while preserving normal navigation otherwise.
web/src/lib/timelines/ScrollToTop.ts	Introduces a small event-based API to request and subscribe to timeline scroll-to-top actions by target key.
web/src/lib/components/Timeline.svelte	Adds an optional scrollToTopTarget prop and registers a scroll-to-top listener on mount to call the existing scrollToTop() behavior.

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[SnowCait]

Thank you!