docs(sdk): orchestrate conversations through existing workspace APIs - #793

Closes #792. Document orchestration through RemoteConversation and RemoteWorkspace: explicit server-side creation with a typed StartConversationRequest, explicit attachment to an existing conversation, title updates, scoped file/command operations, optional asynchronous workspace calls, and runtime credential/lifecycle ownership.

SDK #5010 adds the explicit create/attach methods and scoped workspace operations. Creation sends the canonical request; attachment fetches existing state and never falls back to creation. This guide introduces no separate control-client layer. Publish with that SDK release and Automation profile dispatch. Worker code stays identical in local and Docker workspaces; the dispatcher selects paths and runtime credentials.

Validation: all three Python snippets parse. Live Canvas evidence runs exact Python fences 1 and 2 from this guide revision unchanged: explicit profile creation, title update, byte upload, and the async helper reading the uploaded file with exit 0. A bounded worker using the documented explicit-attachment API also completes a real model task identically in local and Docker workspaces; its task prompt differs from fence 3. The report includes the GIF, screenshots, exact source hashes, and the initial HTTP 500 corrected in SDK4bbab2dd0 without an example-side workaround. It supersedes the historical ordinary-constructor recording.

• I have read and reviewed the documentation changes to the best of my ability.
• If the change is significant, I have run the documentation site locally and confirmed it renders as expected.