chore: merge dev into v2 - #41460

Summary

• port applicable dev changes since the previous synchronization while preserving the V2-only App, Desktop, Core, TUI, SDK, and server architecture
• retain recent App/Desktop behavior, RTL and localization coverage, chronological message/session ordering, full native V2 session export, PTY connect tickets, TUI cursor settings, and shared UI improvements
• keep intentional V2 removals in place and omit legacy layout, V1 protocol branches, old SDK surfaces, and deleted packages
• update the model catalog URL and GitLab provider without importing obsolete Core dependencies

Validation

• typechecks pass: App, Desktop, Core, TUI, Session UI, CLI, Server, Codemode, and Merman
• App unit/browser tests pass: 708 passed, 13 skipped
• TUI tests pass: 608 passed, 5 skipped
• Session UI tests pass: 83 passed
• Core model catalog and GitLab provider tests pass: 19 passed
• Server tests pass: 17 passed, 11 environment-dependent tests skipped
• full CLI suite encountered two lifecycle contention flakes on the shared host; GitHub CI is authoritative
• production App/Desktop build reached final chunk gzip computation but did not finish within the shared-host timeout; GitHub CI is authoritative

Requested by: @Hona (Hona via Slack)