feat(host): adaptive directory-picker default via -auto chooser

Add @deepseek-ai/dsh-host-directory-picker-auto, a node-half-only chooser
that samples the host situation once at boot (bind host via a new
httpServer.host getter, SSH markers, platform, DISPLAY/WAYLAND_DISPLAY)
and mounts the matching dual-face backend (-native or -browse) as a real
Loader entry in the in-memory root tree; the effect disposer removes it.
Entry-level mounting keeps the seam's one-row-swaps-both-faces invariant:
the client module table discovers the mounted backend's browser half
exactly as a config row's. apps/cli now composes -auto as its
directory-picker row; composing a backend row directly remains the pin.

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

@@ -33,7 +33,7 @@ Placement and policy rulings folded into this decision:
 
 ## Consequences
 
-- `cordis.yml` chooses the interaction; `apps/cli` mounts `-browse` (the shipped default — remote-capable picking out of the box), one row having swapped backend and UI together; `-native` remains the host-display alternative.
+- `cordis.yml` chooses the interaction; `apps/cli` mounts the [`-auto` chooser](../feature/2026-07-29-directory-picker-adaptive-default.md), which resolves the host's situation at boot and mounts `-native` or `-browse` itself, one row still swapping backend and UI together; composing a backend row directly pins the interaction.
 - The wire gains `host.listDirectory`/`host.createDirectory` and four error codes; the connection fixture serves a deterministic browse tree and a deterministic `pickDirectory` path for keyless assembled tests.
 - A future interaction (or an Electron provider of the `native` interaction) is one dual-face backend package — no gateway surgery, no ui-workspace edits.
 - `ApiProxyDefaults.pickDirectory` (test-only injection) is gone; tests provide a stub `ctx.directoryPicker` like any other service.