Bug: [lexical-y] With gc on, undoing a format removal while a collaborator applies the same format again takes it off the next character #9683

Lexical version: main at 4a13388 (@lexical/y).

Steps To Reproduce

1. Three clients bind one document holding the paragraphs "ab cd ef" and "next".
2. Client A italicizes "b " and then removes the italic from "b" (two steps). Every client syncs.
3. Offline from each other: client A undoes the removal, and client C italicizes "b" again.
4. The clients sync.

Link to code example: packages/lexical-y/src/__tests__/unit/regressions/Formats.test.ts, describe "F30A-1", case "italic over "b ", italic removed from "b"; the removal undone ‖ "b" italic again". Run LEXICAL_Y_GC=1 pnpm exec vitest run --project unit packages/lexical-y/src/__tests__/unit/regressions/Formats.test.ts -t F30A-1. With LEXICAL_Y_GC=1 (Yjs garbage collection on, as products run) it fails for client id orders 1,2,3 / 3,2,1 / 2,3,1. Without it, it passes. With gc on it fails the same way on main before #9679 (cfcd3c4), so it is not from that change.

The current behavior

With gc on, every client and a fresh reader show "a" "b"[I] " cd ef": the space after "b", which nobody touched after A italicized it, loses its italic.

The expected behavior

"a" "b "[I] "cd ef", as with gc off: both changes give "b" its italic back, and the space keeps the italic from A's first step.

The harness ran every peer with gc off until #9679, so this cell never ran with gc on before; it is pinned as test.fails with gc on until fixed.