fix: skip completion eval when work was delegated to subagent (#179)

When the agent loop called spawn_subagent or invoke_agent, the completion
evaluator now skips rather than re-prompting. The SubagentResultHandler
will deliver the result — re-prompting races with it and produces
duplicate answers (the user sees both the subagent result and the
re-prompted primary response).

Also updates directives to allow direct handling of simple closed
questions that need only 1-2 tool calls. The subagent overhead is
counterproductive for "when does my class end?" style queries.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: rockfordlhotka

src/RockBot.Agent/agent/directives.md

@@ -108,10 +108,15 @@ at a locked input box.
 - Exploratory, research-oriented, or multi-source data tasks.
 - Anything the user asks to do "in the background" or "while we talk."
 
-#### Handle directly (no subagent) only when
+#### Handle directly (no subagent) when
 
 - The response requires **zero tool calls** — purely conversational, drawn from
   context already in your window.
+- The task is a **simple, closed question** that needs one or two tool calls to
+  answer — e.g. "when does my class end?", "what's on my calendar today?",
+  "do I have any unread emails from Bob?" For these, the subagent overhead
+  (spawning, context building, synthesis) takes longer than just calling the
+  tool directly. Answer the question, done.
 - The task requires exactly **one fast local tool call** (a single memory lookup,
   a single working memory read) where the round-trip is under a second.
 - You are synthesizing results that subagents have already returned — reading

src/RockBot.Host/AgentLoopRunner.cs

@@ -219,6 +219,18 @@ public async Task<string> RunAsync(
             if (!enableCompletionEval || maxReprompts == 0 || reprompt == maxReprompts)
                 return result.Response;
 
+            // Skip evaluation when the agent delegated to a subagent. Spawning a
+            // subagent is intentional delegation — the SubagentResultHandler will
+            // synthesize and publish the result. Re-prompting here would race with
+            // that handler and produce duplicate answers.
+            if (chatMessages.Any(m => m.Contents.OfType<FunctionCallContent>()
+                    .Any(fc => fc.Name is "spawn_subagent" or "invoke_agent")))
+            {
+                HostDiagnostics.CompletionCheckSkipped.Add(1);
+                logger.LogInformation("Completion evaluator: SKIPPED (delegated to subagent/agent)");
+                return result.Response;
+            }
+
             // Evaluate whether the response actually completes the original request.
             var (complete, reason) = await EvaluateCompletionAsync(
                 originalUserRequest, result.Response, cancellationToken);