hermes - 💡(How to fix) Fix Desktop sidebar can horizontally overflow while session is running

Bug Description

In the Hermes Desktop app, the left session sidebar can become wider than its container and expose a horizontal scrollbar while the current chat is running/thinking.

This appears to happen when the agent is in the thinking/running state and the sidebar contains normal session rows plus the active/running session indicator. The session list visually stretches horizontally, so the sidebar can be scrolled left/right even though session titles should remain clipped/truncated inside the fixed sidebar width.

Steps to Reproduce

1. Open Hermes Desktop.
2. Open a session with enough history that the left sidebar has a scrollable session list.
3. Send a message and leave the agent in the Thinking / running state.
4. Watch the left session history list while the agent is thinking.

Expected Behavior

The left sidebar should keep a fixed width. Session rows, running indicators, titles, timestamps, and action buttons should truncate or clip inside the sidebar without creating horizontal overflow.

Actual Behavior

While the agent is thinking, the session list can stretch horizontally and a horizontal scrollbar appears at the bottom of the left sidebar. This makes the sidebar feel unstable and allows accidental horizontal scrolling.

Evidence / Observed Environment

• Hermes Desktop on macOS.
• Footer shows v0.15.1 (+3) / commit 96cd37e.
• The affected session was actively running: the sidebar showed a Session running indicator and the chat thread showed Thinking.
• The supplied screenshot clearly shows a horizontal scrollbar at the bottom of the left sidebar, below the session list, while the active session is running.

Related / Possible Regression Context

This looks similar to earlier UI/layout overflow issues where containers needed explicit clipping, min-w-0, truncation, or overflow-x-hidden guards:

• #35520: dashboard/sidebar layout could become unbounded and break scrolling below certain widths.
• #37675: Desktop sticky/user message content was unbounded and could visually cover assistant output.
• Commit 78fa758: responsive Web UI fix added overflow/truncation guards, including overflow-x-hidden, to prevent horizontal scroll/content bleed.

This may be a Desktop sidebar-specific recurrence of the same class of issue: a row child in the virtualized session list, running-state indicator, title/action area, or list container is allowed to use its intrinsic width instead of shrinking within the sidebar.

Suggested Fix Shape

Audit the Desktop sidebar/session row layout for missing width guards, especially around the active/running session row and virtualized session list:

• Ensure flex/grid children that contain text or status affordances have min-width: 0.
• Ensure session titles and status text use truncation/ellipsis inside their row.
• Ensure the sidebar/list scroller clips horizontal overflow (overflow-x: hidden) unless horizontal scrolling is intentionally supported.
• Add a visual/regression test for a running session with long/mixed-language titles and a populated sidebar.