docs(changeset): backfill changesets for unreleased dev changes

[kumilingus]

Description

Backfills the changesets for the changes on dev that are not in any published release — changesets were introduced after these commits landed, so the next release would otherwise ship them without changelog entries.

Most of the dev work turned out to be already released: it was cherry-picked to master (#3446, #3455, …) and covered by the changeset backfill there (#3467), shipping in v4.3.2–v4.3.5. The packages/joint-core source delta between master and dev is empty — no core changeset is needed at all.

What remains unreleased on dev (verified against the published npm artifacts):

PR	Changeset
#3423	<GraphProvider /> — lazy Map-backed immutable cells container, O(change-set) commits, ~2× faster uncontrolled drags (patch)
#3427	useGraph — removeCells() / resetCells() accept a cell collection; adds CellCollection / CellRefList types (minor)

Not covered

• The onCellFocus/onCellBlur part of feat(joint-react): cell focus/blur events, reactive grid, collection setters #3427 — its changeset lives on the feat/paper-focus-events branch (feat(dia.Paper): add focus and blur events; expose them as @joint/react Paper props #3481), where the feature is reworked on top of the new core focus/blur events.
• refactor(joint-react): unify Storybook design system, remove embedded docs #3431 (Storybook design system) — stories and devDependencies only, no releasable code.
• fix: let the guard option veto a blank pointerdown; buttons that click and drag #3438 / fix(joint-react): tolerate a cell removed mid-render (useCell) and assign the forwarded ref during commit (useCombinedRef) #3447 — released via master as fix: let the guard option veto a blank pointerdown; buttons that click and drag #3446 / fix(joint-react): tolerate a cell removed mid-render (useCell) and assign the forwarded ref during commit (useCombinedRef) #3455 (changelog entries in v4.3.3–v4.3.4 and core v4.3.2).

yarn changeset status: @joint/react minor.

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