fix(mcp): report a Failed task's failureReason instead of a bare status

get_task/batch_get_tasks now return failureReason (max_turns|timeout|error|
cancelled|unknown) plus failureTurnsUsed/failureMaxTurns on a Failed task, so
max_turns (worktree usually fine, continue_task) is distinguishable from a
real error (reset_failed_task) without pulling get_task_log's raw NDJSON.
Classified and stamped onto TaskEntity by TaskRunner.MarkFailed via
TaskStateService.FailAsync; TaskRunEntity also keeps the CLI's raw
terminal_reason/result_subtype/errors for deeper diagnosis. reset_failed_task's
description now warns explicitly that it discards the worktree and points at
continue_task for max_turns. Surfaced on the task card's status-chip tooltip.

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

@@ -167,7 +167,7 @@
             <Border Classes="chip"
                     IsVisible="{Binding ShowStatusChip}"
                     Tapped="OnStatusChipTapped"
-                    ToolTip.Tip="{Binding InteractiveChipTooltip}"
+                    ToolTip.Tip="{Binding StatusChipTooltip}"
                     Classes.interactive="{Binding HasInteractiveSession}"
                     Classes.parked="{Binding IsParked}"
                     Classes.running="{Binding Status, Converter={StaticResource EqStatus}, ConverterParameter=Running}"