feat(host): directory-picker capability seam with dialog and browse backends

The web GUI's folder picking was hardwired to one interaction: a native
OS chooser compiled into the gateway, unusable for remote deployments
and swappable only by editing apiproxy source.

Directory picking becomes a three-package capability seam in
packages/host: ctx.directoryPicker returns a discriminated capability —
dialog (the extracted native chooser; host-display only) or browse
(new: one-level listing + child creation over Node stdlib, hidden flags
host-stamped, symlinks followed, ancestry crumbs; remote-capable). The
gateway injects the seam, advertises the kind via
host.describe.directoryPicker, serves host.listDirectory /
host.createDirectory under browse, and answers
directory-picker-unavailable across kinds. cordis.yml is the swap
point; apps/cli keeps dialog mounted, so behavior is unchanged until
the in-app browser PR flips the default. The connection fixture serves
a deterministic browse tree; WorkspacesService gains the browse calls
the browser UI will drive. Decision record:
.agents/notes/implemented/architecture/2026-07-28-directory-picker-capability-seam.md

pnpm-lock.yaml

@@ -212,6 +212,9 @@ importers:
       '@deepseek-ai/dsh-host-apiproxy':
         specifier: workspace:^
         version: link:../../packages/host/apiproxy
+      '@deepseek-ai/dsh-host-directory-picker-dialog':
+        specifier: workspace:^
+        version: link:../../packages/host/directory-picker-dialog
       '@deepseek-ai/dsh-host-webserver':
         specifier: workspace:^
         version: link:../../packages/host/webserver
@@ -2652,6 +2655,9 @@ importers:
       '@deepseek-ai/dsh-commands':
         specifier: workspace:^
         version: link:../../ui/commands
+      '@deepseek-ai/dsh-host-directory-picker':
+        specifier: workspace:^
+        version: link:../directory-picker
       '@deepseek-ai/dsh-llm':
         specifier: workspace:^
         version: link:../../llm/llm
@@ -2699,6 +2705,41 @@ importers:
         specifier: ^4.0.0-rc.7
         version: 4.0.0-rc.7(@cordisjs/plugin-include@1.0.4)(@cordisjs/plugin-loader@1.0.0-rc.5)
 
+  packages/host/directory-picker:
+    devDependencies:
+      '@deepseek-ai/dsh-invariants':
+        specifier: workspace:^
+        version: link:../../support/invariants
+      cordis:
+        specifier: ^4.0.0-rc.7
+        version: 4.0.0-rc.7(@cordisjs/plugin-include@1.0.4)(@cordisjs/plugin-loader@1.0.0-rc.5)
+
+  packages/host/directory-picker-browse:
+    dependencies:
+      '@deepseek-ai/dsh-host-directory-picker':
+        specifier: workspace:^
+        version: link:../directory-picker
+    devDependencies:
+      '@deepseek-ai/dsh-invariants':
+        specifier: workspace:^
+        version: link:../../support/invariants
+      cordis:
+        specifier: ^4.0.0-rc.7
+        version: 4.0.0-rc.7(@cordisjs/plugin-include@1.0.4)(@cordisjs/plugin-loader@1.0.0-rc.5)
+
+  packages/host/directory-picker-dialog:
+    dependencies:
+      '@deepseek-ai/dsh-host-directory-picker':
+        specifier: workspace:^
+        version: link:../directory-picker
+    devDependencies:
+      '@deepseek-ai/dsh-invariants':
+        specifier: workspace:^
+        version: link:../../support/invariants
+      cordis:
+        specifier: ^4.0.0-rc.7
+        version: 4.0.0-rc.7(@cordisjs/plugin-include@1.0.4)(@cordisjs/plugin-loader@1.0.0-rc.5)
+
   packages/host/webserver:
     dependencies:
       schemastery: