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.

.agents/notes/implemented/architecture/2026-07-28-directory-picker-capability-seam.md

@@ -30,7 +30,7 @@ Placement and policy rulings folded into this decision:
 
 ## Consequences
 
-- `cordis.yml` chooses the interaction; `apps/cli` currently mounts `-dialog` (unchanged behavior), and the in-app browser PR flips the default to `-browse` with the GUI branching on `describe`.
+- `cordis.yml` chooses the interaction; `apps/cli` currently mounts `-dialog` (unchanged behavior). The GUI already gates its dialog affordance on `describe.directoryPicker` (non-`dialog` kinds hide it); the in-app browser PR flips the default to `-browse` and adds the browse UI.
 - The wire gains `host.listDirectory`/`host.createDirectory`, four error codes, and the `describe.directoryPicker` field; the connection fixture serves a deterministic browse tree for keyless assembled tests.
 - A future interaction (or an Electron `dialog` provider) is one backend package plus a client branch — no gateway surgery.
 - `ApiProxyDefaults.pickDirectory` (test-only injection) is gone; tests provide a stub `ctx.directoryPicker` like any other service.