[$75] Update ghost text in Expense Threads / Reports

[thienlnam]

Slack Thread Context: https://expensify.slack.com/archives/C090U774ZH7/p1766084764506399?thread_ts=1766084764.506399&cid=C090U774ZH7

What the problem is:
The current ghost/placeholder text in report and expense comment boxes is generic: "Write something". The team agreed this does not communicate that Concierge AI can take actions based on the comment, so users may not realize Concierge can create or update expenses.

What the expected output is:
Replace the generic placeholder with copy that clearly signals Concierge can act. The agreed candidate phrases to surface randomly are:

Ask Concierge AI to create an expense...
Ask Concierge AI to update an expense...
Ask Concierge AI to correct an expense...

This should only be the placeholder text within expense threads / reports

Issue Owner

Current Issue Owner: @

Upwork Automation - Do Not Edit

• Upwork Job URL: https://www.upwork.com/jobs/~022001806632076083538
• Upwork Job ID: 2001806632076083538
• Last Price Increase: 2025-12-29
• Automatic offers:
• huult | Reviewer | 110005897

Issue Owner

Current Issue Owner: @deetergp

[melvin-bot]

Triggered auto assignment to Contributor-plus team member for initial proposal review - @rojiphil (External)

[melvin-bot]

Triggered auto assignment to @mallenexpensify (NewFeature), see https://stackoverflowteams.com/c/expensify/questions/14418#:~:text=BugZero%20process%20steps%20for%20feature%20requests for more details. Please add this Feature request to a GH project, as outlined in the SO. Remember to draft any necessary HelpDot updates by following the instructions here.

[melvin-bot]

⚠️ It looks like this issue is labelled as a New Feature but not tied to any GitHub Project. Keep in mind that all new features should be tied to GitHub Projects in order to properly track external CAP software time ⚠️

[melvin-bot]

Triggered auto assignment to Design team member for new feature review - @dubielzyk-expensify (NewFeature)