Desktop app: @-mention renders literal "@[SessionName]" bracket text on first insert, needs delete+reselect to show as chip/link

Description

In the Claude Code desktop app, typing @ in the chat input to mention another local session and selecting one from the autocomplete list inserts the mention as literal bracket text — @[SessionName] — instead of rendering as a styled mention chip/link.

Deleting the inserted text and re-selecting the same session from the picker a second time then renders it correctly as a chip/link.

Steps to reproduce

1. Open the Claude Code desktop app with at least one other local session running.
2. In the chat input, type @ to open the session-mention autocomplete.
3. Select a session from the list (e.g. "Athenaeum").
4. Observe: the input shows literal text @[Athenaeum] rather than a rendered chip.
5. Delete the inserted mention and repeat step 2–3 for the same session.
6. Observe: this second time it renders correctly as a chip/link.

Expected behavior

Per the cross-session messaging docs, a selected mention should render as @session-name (styled), not as literal @[SessionName] bracket text.

Actual behavior

First selection inserts raw @[SessionName] text. Only a subsequent delete + re-select renders the proper chip/link — suggesting the chip-swap step (likely an async session-ID resolution) doesn't fire on the initial insert event, only on a later edit event.

Environment

• Claude Code desktop app (macOS)
• Feature: cross-session @-mention / ListAgents-based mention picker

Additional context

Checked official docs and searched existing issues first — found no existing report of this specific symptom, and no documentation describing bracket text as intended syntax at any stage.