feat(web-search-deepseek): resolve provider options from the settings section

The provider now takes a thunk rather than a value: it projects the
authoritative section per search, so a stored endpoint, model, or key
reference reaches the next call without re-registering the provider — which
would make the seam's provider selection observable as a flicker.

apiKey already carries role('secret'), so the section is safe to describe:
the literal never rides a response in any layer and a configuration surface
learns only that a key is set.

packages/web/web-search-deepseek/package.json

@@ -30,6 +30,7 @@
     "@deepseek-ai/dsh-environment": "^0.0.1",
     "@deepseek-ai/dsh-invariants": "^0.0.1",
     "@deepseek-ai/dsh-session": "^0.0.1",
+    "@deepseek-ai/dsh-settings": "^0.0.1",
     "@deepseek-ai/dsh-web": "^0.0.1",
     "cordis": "^4.0.0-rc.7"
   },
@@ -43,6 +44,7 @@
     "@deepseek-ai/dsh-environment": "workspace:^",
     "@deepseek-ai/dsh-invariants": "workspace:^",
     "@deepseek-ai/dsh-session": "workspace:^",
+    "@deepseek-ai/dsh-settings": "workspace:^",
     "@deepseek-ai/dsh-web": "workspace:^",
     "cordis": "^4.0.0-rc.7"
   }