Sidebar project grouping is inconsistent; add a way to disable directory-based grouping

Environment: Claude Code desktop app, sidebar redesign (April 2026), macOS 15.5

Problem

Since the April 2026 sidebar redesign, sessions are grouped by project/working directory in a way that's inconsistent between projects:

• Some projects get their own group header by working directory, even when they share a project name with others.
• Other projects are merged into one flat list under a single header, despite those sessions having distinct working directories too.

In my case each project has exactly one session. So grouping buys nothing — it just wraps a single item in its own header, roughly doubling the vertical space per project and pushing everything else out of view. Combined with the inconsistency (no way to predict whether a given project will get its own header or be merged into a shared one), the sidebar becomes hard to scan and administer across many small projects.

Requested

Either of these would resolve it:

1. A setting to disable directory-based grouping and fall back to a flat project list, or
2. Documented, consistent rules for what determines the grouping, so the behavior is predictable.

Alternatively, suppressing the group header when a group contains only one session would fix most of the noise on its own.

Expected: grouping follows one rule across all projects, or is user-controllable.

Actual: grouping differs per project with no visible cause, and single-session projects each consume a header plus a row.