Open In at the Session header targets the original checkout, not the working directory (worktree sessions)

[sirwolfgang]

Symptom

A Session that moves checkouts still opens its original project from the header's Open In button. That covers the New worktree option, create_worktree, and working_directory.

Cause

The header action in client-ui-open-in-app reads the Session list summary:

const { sessionId, useSessions } = props;
const cwd = useSessions((state) => state.byId[sessionId]?.cwd);

That cwd is fixed from the immutable Session header. The live directory is the workingDirectory projection.

Fix we carry

Read the projection first and keep the summary as the fallback — two lines in lib/client.js:

const worktree = useProjection("workingDirectory");
const summary = useSessions((state) => state.byId[sessionId]?.cwd);
const cwd = typeof worktree === "string" && worktree.length > 0 ? worktree : summary;

Reproduction

1. Start a Session with New worktree checked.
2. Let one turn finish so the header renders.
3. Click Open In: the parent checkout opens, not .agents/worktrees/<name>.

The same stale value reaches any other surface that reads cwd from the Session summary rather than the projection — #12273 is the same class of bug for forge change-request bindings, which have no checkout dimension at all.