fix(host,client): gate the picker affordance on the advertised kind; reject non-absolute browse paths

ds-review-bot round 2. The workspace UI never consulted the advertised
directoryPicker kind: under a browse (or merge-added) backend it still
rendered 'Open local folder…' and called pickDirectory(), which the host
answers with directory-picker-unavailable. The create flow now reads
directoryPickerKind() per menu open and renders the dialog affordance only
under 'dialog' — browse (until its in-app browser UI lands) and unknown
kinds hide the entry, realizing the seam's documented default; a keyless
workspace-flow snapshot pins the hidden entry over the browse fixture.

The browse backend also resolved wire paths, silently rebasing '' or
relative parents under the host process cwd; both primitives now reject
non-absolute explicit paths with their business codes, and the seam JSDoc
carries the contract.

packages/client/ui-workspace/src/client/WorkspaceBrowser.tsx

@@ -254,6 +254,7 @@ export function WorkspaceBrowser({
   insertSessionBefore,
   createWorkspace,
   pickDirectory,
+  directoryPickerKind,
 }: WorkspaceBrowserProps) {
   const workspaces = useWorkspaces(state => state.items)
   const groupBy = useStore(s => s.groupBy)
@@ -372,6 +373,7 @@ export function WorkspaceBrowser({
           useWorkspaces={useWorkspaces}
           createWorkspace={createWorkspace}
           pickDirectory={pickDirectory}
+          directoryPickerKind={directoryPickerKind}
           onPick={(workspaceId) => {
             setWsPickerOpen(false)
             startSession(workspaceId)