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.Data/Migrations/ClaudeDoDbContextModelSnapshot.cs

@@ -471,6 +471,18 @@ namespace ClaudeDo.Data.Migrations
                         .HasColumnType("TEXT")
                         .HasColumnName("description");
 
+                    b.Property<int?>("FailureMaxTurns")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("failure_max_turns");
+
+                    b.Property<string>("FailureReason")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("failure_reason");
+
+                    b.Property<int?>("FailureTurnsUsed")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("failure_turns_used");
+
                     b.Property<DateTime?>("FinishedAt")
                         .HasColumnType("TEXT")
                         .HasColumnName("finished_at");
@@ -633,6 +645,10 @@ namespace ClaudeDo.Data.Migrations
                         .HasColumnType("TEXT")
                         .HasColumnName("error_markdown");
 
+                    b.Property<string>("Errors")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("errors");
+
                     b.Property<int?>("ExitCode")
                         .HasColumnType("INTEGER")
                         .HasColumnName("exit_code");
@@ -664,6 +680,10 @@ namespace ClaudeDo.Data.Migrations
                         .HasColumnType("TEXT")
                         .HasColumnName("result_markdown");
 
+                    b.Property<string>("ResultSubtype")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("result_subtype");
+
                     b.Property<int>("RunNumber")
                         .HasColumnType("INTEGER")
                         .HasColumnName("run_number");
@@ -685,6 +705,10 @@ namespace ClaudeDo.Data.Migrations
                         .HasColumnType("TEXT")
                         .HasColumnName("task_id");
 
+                    b.Property<string>("TerminalReason")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("terminal_reason");
+
                     b.Property<int?>("TokensIn")
                         .HasColumnType("INTEGER")
                         .HasColumnName("tokens_in");