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.

packages/host/webserver/README.i18n.yaml

@@ -2,5 +2,5 @@
 # side as of the last confirmed-consistent state. Both languages carry equal authority;
 # after editing either side, bring the other along and re-record with:
 #   pnpm run verify-translation-pairing --write packages/host/webserver/README.md
-README.md: e715e4452ddb808f36e6b097eee0fda7b8d0bfb0
-README.zh.md: 05e7e10d7815c8f26bb90597b38b7c6b83a86dbc
+README.md: ace8c09e43dd8544a28d300f97b04610be78bc69
+README.zh.md: b9948e3d387a5da393ff62b9eeacfe310516f46a