Rename threads and side chats inline instead of in a dialog

[jsgrrchg]

Problem

Renaming a thread opened a modal "Rename session" dialog, both from the left sidebar's chat menu and for side chats under the file tree. There was no way to rename a row directly where it sits.

Change

• Double-click a session row in the left sidebar, or a side chat row in the explorer's Chats footer, to swap its title for an in-place field with the current name selected.
• The chat menu's Rename (label drops the ellipsis, since it no longer opens a dialog) and the /rename command open the same field.
• Enter or blur saves a changed, non-empty title. Escape cancels. Clicking inside the field places the caret instead of opening the chat or starting a drag.
• The modal dialog is removed.

Hidden rows are revealed first

A rename started without touching the row (/rename, or Rename from a side chat's tab) could previously target a row that wasn't on screen, leaving an invisible field holding focus. Now the row is revealed before the field opens:

• A collapsed Pinned, Sessions, custom section, or device/project group opens with its usual disclosure motion. Expanding a synced custom section goes through the normal section change.
• The Archived shelf opens and pages forward (in "Show more" steps) to include the row.
• A collapsed sidebar expands.
• The sidebar scrolls the row clear of its edge fades, following the disclosure while it opens.
• The explorer's Chats section opens, pages, and scrolls to the side chat the same way.

When the row can't be shown, no field opens and the sidebar notice says why:

• The project filter hides it. The filter is left alone.
• A synced section can't be edited yet. The existing "still syncing" notice is shown.
• It's a side chat of a chat that isn't open.

Implementation notes

• Shell owns a single ChatRename (chat id, which surface draws it, the input, commit-on-blur subscription). It replaces RenameChatDialog. The explorer receives the field through FilesSurface::set_chat_rename and emits FilesEvent::RenameChildChat on double-click.
• Both lists render the same chat_title_editor (a single-line ComposerInput at the row title's 13/17 metrics). ComposerInput::select_all_text is now public so the field opens with the name selected.
• Disclosure motions need the body height, which is only known at render time. A reveal queues the disclosure key, and each section starts its opening motion on the next render.
• archived_sidebar_chats and the device/project group key helpers are extracted so the reveal and the render share one definition.

Testing

• cargo test -p zeron-ui --lib: 1503/1504 passed. The one failure was markdown::render::tests::markdown_drag_crosses_cells_and_formatted_blocks_in_document_order, which passes when run alone; it only fails when the suite runs in parallel. shell::files_panel::workspace_tests::files_panel_workspace_navigation_and_external_updates also failed in an earlier full run and fails on main without this change.
• New tests in shell/chat_rename_tests.rs and files/sections.rs cover:
  • double-click editing
  • Escape
  • an unchanged title
  • Enter and blur commits
  • menu or /rename opening
  • collapsed Pinned, Sessions, sidebar, project group, and custom section
  • Archived paging
  • scrolling a far row into view
  • the project-filter refusal
  • the explorer's collapsed, paged Chats section
• Not yet checked by hand in the running app.

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[katulevskiy]

works in compact mode?

[jsgrrchg]

works in compact mode?

yes it does, i test it manually

[wingleeio]

Reviewed the full diff: UI-only (no new deps, unsafe, I/O, network or process code); renames still go through the same renameChat mutation with a trimmed, non-empty title, now skipped when unchanged or the chat is gone. Re the compact-mode question: compact is the default, so the sidebar tests already ran compact; added a test covering both compact and full rows (field sits in the row, row height unchanged). 1520/1520 UI tests green.