[FEATURE] Show each session's working directory in the desktop sidebar

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

I often have several sessions open on the same repo, each in a different folder — usually git worktrees for parallel branches. In the desktop app's session sidebar, every row shows only the session title. Sessions from different worktrees of the same repo look identical and collapse under the same project group, so there is no way to tell which folder a given session is actually working in without opening it.

Proposed Solution

Show the working directory on each session row — the full path isn't necessary; the last path segment (or the shortest distinguishing suffix when several sessions share a repo) would be enough. A secondary line or a muted inline suffix would both work. At minimum:

• an option/setting to enable per-row directory display, and
• the working directory shown prominently somewhere for the currently active session.

Alternative Solutions

• Manually renaming sessions to include the folder name — works but is tedious and rots as sessions accumulate.
• Codex's session list shows the folder/project context per session, which makes juggling multiple checkouts of one repo much easier.

Priority

Medium - Would be very helpful

Feature Category

Other

Use Case Example

1. I'm working on a 3-PR stack in one repo, each PR in its own worktree.
2. I have a session open in each worktree, plus one in the main checkout.
3. The sidebar shows four sessions under one project group with similar titles.
4. With this feature I could see at a glance which session belongs to which worktree instead of opening each one to check.

Additional Context

Deliberately scoped to displaying the directory only. Sidebar grouping behavior is already covered by existing issues: #84040 (directory-based grouping is inconsistent / needs a toggle), #68171 (grouping into folders/collections), #86232 (nested sub-groups), #81914 (custom groups). This request complements those: whatever the grouping rules end up being, same-repo worktree sessions still need a visible per-session directory to be distinguishable.