docs: sync react v14 migration trackers (#3037)

### 🎯 Goal

Keep the internal React v14 migration trackers in sync with the latest
confirmed master-branch changes and the matching docs refresh in
docs-content.

Linked docs PR: GetStream/docs-content#1104

### 🛠 Implementation details

- continue the breaking-change audit from the latest recorded snapshot
through current master
- add the newly confirmed `MessageComposer*`, `ChannelListItem*`, and
`MessageListNotifications` removal items to
`ai-docs/breaking-changes.md`
- update `ai-docs/docs-plan.md` to reflect the follow-up docs work, then
mark those work items resolved after the docs sweep landed locally
- refresh the audited head / future-mining starting point so the next
audit can continue from the right commit window

### 🎨 UI Changes

None. Tracker-only change.

Author: oliverlaz