refactor(ui): remove pick-up-in-terminal, keep ConPTY as the single session entry

Two context-menu entries opened a Claude session for the same task via different
mechanisms (embedded ConPTY vs. an external wt terminal). Drop the external-terminal
path entirely, including its worker hub method, launcher plumbing, and localization
keys, since the embedded ConPTY session already covers every case it did.

src/ClaudeDo.Ui/Views/Islands/TaskRowView.axaml

@@ -58,9 +58,6 @@
             <Separator/>
             <MenuItem Header="{loc:Tr tasks.ctxOpenConPtySession}"
                       Click="OnOpenConPtySessionClick"/>
-            <MenuItem Header="{loc:Tr tasks.ctxPickUpInTerminal}"
-                      Click="OnPickUpInTerminalClick"
-                      IsVisible="{Binding CanPickUpInTerminal}"/>
             <MenuItem Header="{loc:Tr tasks.ctxOpenPlanningSession}"
                       Click="OnOpenPlanningSessionClick"
                       IsVisible="{Binding CanOpenPlanningSession}"/>