feat(worker-mcp): raise wait_for_task_change timeout, expose queue slot state

MaxTimeoutSeconds was 170s against runs that take tens of minutes, forcing
a dozen full-context wait rounds per long-running batch. Raise it to 900s
and raise MCP_TOOL_TIMEOUT in lockstep (ClaudeProcess + every
InteractiveLaunchSpecService launch spec) to 930000ms so the client
connection actually stays open that long instead of aborting first.

Add get_queue_state (QueueStateMcpTools): configured vs. effective
parallel-slot count (via QueueService.GetSlotCountsAsync, extracted from
the former GetEffectiveMaxParallelAsync), active slots with taskId +
startedAt including the run_task_now override slot, and queued tasks in
pick order -- so a caller can observe queue occupancy instead of inferring
it from maxParallelExecutions.

src/ClaudeDo.Worker/Program.cs

@@ -302,6 +302,7 @@ if (cfg.ExternalMcpPort > 0)
     externalBuilder.Services.AddScoped<LifecycleMcpTools>();
     externalBuilder.Services.AddScoped<AppSettingsMcpTools>();
     externalBuilder.Services.AddScoped<TaskWaitMcpTools>();
+    externalBuilder.Services.AddScoped<QueueStateMcpTools>();
     externalBuilder.Services.AddSingleton(app.Services.GetRequiredService<AttachmentStore>());
     externalBuilder.Services.AddScoped<TaskAttachmentRepository>();
     externalBuilder.Services.AddScoped<AttachmentMcpTools>();
@@ -317,6 +318,7 @@ if (cfg.ExternalMcpPort > 0)
         .WithTools<LifecycleMcpTools>()
         .WithTools<AppSettingsMcpTools>()
         .WithTools<TaskWaitMcpTools>()
+        .WithTools<QueueStateMcpTools>()
         .WithTools<AttachmentMcpTools>();
     externalBuilder.WebHost.UseUrls($"http://127.0.0.1:{cfg.ExternalMcpPort}");