Fix live user message metadata during streaming

[Paul Lizer (paullizer)]

Summary

• emit a nonterminal user_message_persisted event after durable storage across standard, document-action/analyze, image-generation, and collaboration streams
• reconcile temporary user-message IDs immediately so metadata loads while the assistant is still running
• preserve finalized metadata through success, error, cancellation, disconnect, recovery, and manual reattachment states
• gate Mask/Edit/Delete/Retry until terminal completion to prevent mutations of in-flight turns
• add functional and Playwright regression coverage, fix documentation, release notes, and app version 0.250.202

Validation

• 12 focused live-metadata functional regressions passed after merging current Development
• live metadata Playwright coverage passed
• newly merged exhaustive-row regression suites passed when run in isolated processes
• JavaScript/Python syntax and diff checks passed
• one long upstream scale test has a pre-existing NameError in files identical to Development

Fixes #1244