refactor: add mcp source client facade

docs/current_roadmap.md

@@ -238,6 +238,10 @@ implementation state.
       `McpSdkAdapter` is now canonical in `wf_sources_mcp`; `wf_mcp.sdk.*`
       remains a compatibility shim for old imports. Persistent runtime is still
       tool-call-only.
+    - Completed: shared `McpSourceClient` facade introduced in
+      `wf_sources_mcp.client`. The one-shot SDK adapter delegates MCP operation
+      calls and conversion through the facade; persistent runtime remains
+      tool-call-only until a separate owner-task routing slice.
   - Auth/source secrets boundary: keep registry desired state separate from
     upstream credentials, and surface missing auth as validation diagnostics.
     The contract is now specified in

docs/superpowers/specs/2026-06-03-long-lived-workflow-api-boundary.md

@@ -107,7 +107,11 @@ First slices should move leaf modules only and leave `wf_mcp` re-export shims:
    compatibility shim. This does not expand persistent runtime; the next
    design slice should unify one-shot and persistent client operation handling
    behind a shared source-client facade.
-9. Upstream transport/discovery/session services.
+9. Complete: shared `McpSourceClient` facade introduced in
+   `wf_sources_mcp.client`. `McpSdkAdapter` now delegates operation handling to
+   this facade. Persistent runtime still exposes only `call_tool`; expanding it
+   requires a separate owner-task request routing slice.
+10. Upstream transport/discovery/session services.
 
 Each slice should add import-direction tests so the new source-provider package
 does not depend on `wf_mcp.workflow_surface`, `wf_mcp.admin_surface`,