Trailing block normalize inserts must run without suggestions

Problem

In suggestion mode, typing inside a table could create an unrelated Add: Paragraph suggestion under the table.

The extra suggestion came from the editor's trailing-block normalization, not from the user's input.

Root cause

TrailingBlockPlugin inserted its fallback paragraph directly inside normalizeNode.

That insert ran through the normal editor transform pipeline, so suggestion tracking could record it as a user change when the editor was in suggestion mode.

Fix

Make trailing-block insertion pluggable instead of hard-coding the transform:

add an optional insert(editor, { at, insert, type }) hook to TrailingBlockPlugin
keep the default behavior unchanged when no hook is provided
in app editor kits, configure that hook to wrap the insert with SuggestionPlugin.withoutSuggestions(insert)

This keeps packages/utils generic while letting the app opt specific normalize-generated inserts out of suggestion tracking.

Verification

These checks passed:

bash

bun test packages/utils/src/lib/plugins/trailing-block/withTrailingBlock.spec.tsx
pnpm install
pnpm turbo build --filter=./packages/utils --filter=./apps/www
pnpm turbo typecheck --filter=./packages/utils --filter=./apps/www
pnpm lint:fix

Browser check:

on http://127.0.0.1:3051/blocks/playground
switch the editor to Suggestion
type 1 inside a table cell
confirm the page does not show Add: Paragraph

Prevention

When a plugin inserts nodes during normalization, do not assume those transforms should be tracked like direct user edits.

Prefer a small escape hatch at the plugin boundary, then let the app layer decide whether that insert should run inside withoutSuggestions, withoutNormalizing, or another wrapper.