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.

tests/ClaudeDo.Worker.Tests/Runner/InteractiveLaunchSpecServiceTests.cs

@@ -241,7 +241,7 @@ public sealed class InteractiveLaunchSpecServiceTests : IDisposable
         Assert.Equal(_worktreeDir, spec.Cwd);
         Assert.Equal(_claudeStubPath, spec.Exe);
         Assert.Equal(new[] { "--resume", "sess-123" }, ArgsAfterEffort(spec));
-        Assert.Equal("200000", spec.Env["MCP_TOOL_TIMEOUT"]);
+        Assert.Equal("930000", spec.Env["MCP_TOOL_TIMEOUT"]);
     }
 
     [Fact]
@@ -400,7 +400,7 @@ public sealed class InteractiveLaunchSpecServiceTests : IDisposable
         Assert.Equal(_tempDir, spec.Cwd);
         Assert.Equal(_claudeStubPath, spec.Exe);
         Assert.Empty(ArgsAfterEffort(spec));
-        Assert.Equal("200000", spec.Env["MCP_TOOL_TIMEOUT"]);
+        Assert.Equal("930000", spec.Env["MCP_TOOL_TIMEOUT"]);
         Assert.Empty(_seeder.Calls);
     }
 
@@ -534,7 +534,7 @@ public sealed class InteractiveLaunchSpecServiceTests : IDisposable
         Assert.Contains(briefPath, kickoff);
         Assert.DoesNotContain('\n', kickoff);
 
-        Assert.Equal("200000", spec.Env["MCP_TOOL_TIMEOUT"]);
+        Assert.Equal("930000", spec.Env["MCP_TOOL_TIMEOUT"]);
     }
 
     [Fact]