Web project picker does not load sessions for selected project #31493

Description

When opencode web is started from one project, the web app can list other known projects, but selecting one of those projects can keep the session list scoped to the startup project.

In the API, /project returns the known projects, but /session had no explicit project selector, so web session loading depended on the server startup/current instance context instead of the project selected in the UI.

Expected behavior

Selecting a project in the web UI should load that project's root sessions, even when the web server was started from a different working directory.

Reproduction

1. Start opencode web from project A.
2. Create sessions from the CLI in project B.
3. Open the web app and select project B.
4. The project list includes project B, but the session list can still show project A/startup-context sessions.

OpenCode version

1.16.2

Operating System

Linux