cleanup(web): give adding a Workspace one route

Both Workspace surfaces offered "Open local folder…" and "Create a new
workspace" for one outcome. The browse occupant already carries its own
New folder affordance, so picking a directory covered creating one; the
name dialog only added a second vocabulary and a create target the
operator could neither see nor choose.

The surviving entry is named after the outcome — "Add workspace…" — and a
menu now appears only where there is something to choose between: with no
Workspace listed (the add-only sidebar header, or an empty hero list) the
anchor gesture raises the directory flow directly instead of a one-row
popover. An empty list counts as final only after the list baseline lands,
and a composition with no directory-flow occupant hides the sidebar button
rather than offering a dead one.

WorkspaceCreateFlow becomes WorkspacePickFlow (createOnly -> addOnly) and
the injected createWorkspace narrows to { path }. The host's
workspace.create({ name }) branch and `dsh web --workspace-root` lost their
last product consumer; both are marked at the call site for a follow-up.

packages/host/apiproxy/src/api-proxy.ts

@@ -1591,6 +1591,11 @@ export function createApiProxy(ctx: Context, defaults: ApiProxyDefaults): ApiPro
       // Exactly one of path/name arrives (schema refine). Existing-folder
       // adoption reuses its canonical path; create-by-name rejects a name
       // already present in the registry.
+      // TODO: the create-by-name branch lost its last product consumer when
+      // the Web picker collapsed onto the directory flow
+      // (.agents/notes/implemented/simplification/2026-07-31-one-route-to-add-a-workspace.md).
+      // Delete it with the wire schema's `name` member, this `defaults.workspaceRoot`,
+      // and the `dsh web --workspace-root` flag that exists only to feed it.
       async create(request) {
         const { payload } = request
         let path: string