fix: handle scheduled roots during async batch rebasing

[svelte-triage-bot]

Fixes #18675.

When one async batch commits, another batch can legitimately already have roots scheduled for a later flush. Batch rebasing incorrectly treated this as an invariant violation and could eagerly traverse work that was already scheduled.

Record whether the target batch already has scheduled work before marking rebase dependencies, and only eagerly traverse roots newly created by that marking when no flush is already pending.

Adds a runtime-runes regression covering a branch mounted after initial render with $effect.pending(), an awaited each block, bind:this, and a second awaited expression.

[pkg-svelte-dev]

Install the latest version of svelte from 3abb714:

pnpm add https://pkg.svelte.dev/svelte/c/3abb714b260f432dda4e57125b9eba012fb1c04f

Open in pkg.svelte.dev: https://pkg.svelte.dev/repos/svelte/pr/18676

Note

This PR is from a fork. A maintainer must approve approve each commit before it can be built and installed.

[changeset-bot]

⚠️ No Changeset found

Latest commit: 3abb714

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