Title: Bring Confluence's spreadsheet-style Excel viewer to Jira attachment previews

Description:

Confluence Cloud recently received an improved Excel file viewer that renders spreadsheets in a proper grid/spreadsheet layout with tab support, scrollable data, and visible gridlines — essentially how users expect to see Excel files (see A new way to view Excel files in Confluence).

Jira Cloud's attachment previewer, however, still renders Excel files in a paginated, print-style layout. This makes it very difficult to review spreadsheet data without downloading the file first.

Current behavior:

• Excel attachments in Jira are rendered as paginated "printed" pages

• No gridlines, no sheet tabs, no scrollable spreadsheet view

• Users must download the file to properly view the data

Expected behavior:

• Excel attachments in Jira should render using the same spreadsheet-style viewer already available in Confluence

• Grid layout with visible cell borders

• Sheet tab navigation for multi-sheet workbooks

• Scrollable, zoomable data view

Why this matters:

• Downloading files just to view them is not user-friendly and breaks workflow

• The technology already exists within Atlassian's platform (Confluence Cloud)

• Many competing tools offer proper inline spreadsheet rendering

• Teams that work with Excel data in Jira (logistics, finance, operations) are particularly impacted

Related tickets:

• JRACLOUD-64979 — marked as fixed, but only enabled basic preview, not spreadsheet-style rendering

• CONFCLOUD-74094 — Excel grid display issues in Confluence, showing the viewer is still evolving

Request: Please bring the Confluence Excel viewer experience to Jira Cloud attachment previews for feature parity across the Atlassian platform.