Follow-up to v0.51.819 which removed the export button from the composer footer
(it tripped the footer overflow-collapse, hiding model/workspace labels). Per
design consult (Fable) + ChatGPT/Open-WebUI convention, export now lives in the
per-conversation sidebar three-dot action menu, right after Duplicate:
- exportSessionHTML(session) parameterized (was active-session-only); Settings
button now wired ()=>exportSessionHTML() and still exports the active session
- new _appendSessionExportHtmlAction() added after Duplicate + in the read-only
early-return branch (export is non-mutating; imported sessions re-exportable)
- exports THAT row's conversation, not just the active one
- download icon added to ICONS; session_export_html[_desc] added to 14 locales
- Settings HTML button retained as secondary data-management entry