Tracker: mcpdo client issues for v2.10.0 #2570

Goal

Collect the open mcpdo client issues scheduled for v2.10.0 in one place, so the client's share of the milestone can be read and worked as a unit.

Scope

Issues for the mcpdo session client (#1432) and the work around it — its shared surface and its documentation.

The Sub-issues panel on this issue is the canonical list.

Done when

Every sub-issue is closed (or moved out of v2.10.0 with a note here).

Priority: Medium — severity 3 (a collection of real gaps/bugs in one client) + urgency 3 (wanted this milestone) + 1 (milestoned) = 7.