Session Badge on Issue Boards
## Summary
Extend session visibility from the work item detail view to the issue board by adding a session badge to the issue card. The badge surfaces whether an issue has active or recent sessions without requiring users to open the item. This reuses the data contract from the existing Session Widget for Issues/MRs work
## Problem
The session widget on work items and MRs gives users observability once they're inside the object, but the issue board is where planners, managers, and contributors triage work at scale. Today on the board:
* You can't tell which issues have agent activity without opening them
* You can't spot issues waiting on input or failed sessions at a glance
* Triage and prioritization don't account for in-flight agent work
* Duplicate work is still possible because session activity isn't surfaced where work is planned
## Proposal
### 1. Session badge on issue board cards
Add a badge beside the status badge on each issue card. The badge shows the session icon with a count and uses colour to reflect the most recent session state across all sessions on that issue.
{width=900 height=568}
### 2. Hover: session breakdown popover
On hover, the badge opens a popover listing sessions on the issue with:
* Session ID and flow type
* Status
{width=288 height=172}
### 3. Click behaviour
Clicking the badge navigates to the work item and scrolls to the session widget, where users can click into individual sessions.
For issues with a single session, we may link directly to that session instead of the work item. To be confirmed during build.
## Design
[Claude Design mockup](https://claude.ai/design/p/019e2ca1-be92-7b6c-a95d-ad04806f7602?file=index.html&via=share)
issue