refactor(host): rename the directory-picker dialog backend and kind to native

The browse interaction also presents a dialog (the in-app modal), so 'dialog'
failed to discriminate the two capability kinds; 'native' names where the
chooser runs. Package directory-picker-dialog -> directory-picker-native, kind
'dialog' -> 'native', with every seam/gateway/client/doc reference updated and
the seam Agent Note's naming rationale rewritten to match.

apps/cli/cordis.yml

@@ -236,7 +236,7 @@
 # Directory-picking backend consumed by the gateway's host.* picker RPCs.
 # Swap point: mount '-browse' instead for the in-app browser (remote-capable).
 - id: directory-picker
-  name: '@deepseek-ai/dsh-host-directory-picker-dialog'
+  name: '@deepseek-ai/dsh-host-directory-picker-native'
 
 - id: api-gateway
   name: '@deepseek-ai/dsh-host-apiproxy'

apps/cli/package.json

@@ -48,7 +48,7 @@
     "@deepseek-ai/dsh-fs-local": "workspace:^",
     "@deepseek-ai/dsh-fs-policy": "workspace:^",
     "@deepseek-ai/dsh-host-apiproxy": "workspace:^",
-    "@deepseek-ai/dsh-host-directory-picker-dialog": "workspace:^",
+    "@deepseek-ai/dsh-host-directory-picker-native": "workspace:^",
     "@deepseek-ai/dsh-host-webserver": "workspace:^",
     "@deepseek-ai/dsh-llm": "workspace:^",
     "@deepseek-ai/dsh-llm-deepseek": "workspace:^",