feat: implement processDomainConsultation main handler

- Add full conversation flow with session management
- Handle tool call execution
- Support __PASSTHROUGH__ and __SESSION_END__ markers
- Add hasDomainSession helper for routing
- Export executeDomainAction from domain-tool.ts

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/agents/domain-agent.ts

@@ -593,10 +593,93 @@ export async function processDomainConsultation(
   userMessage: string,
   env: Env
 ): Promise<string> {
-  // TODO: Implement in Task 8
-  logger.info('도메인 상담 처리 요청 (미구현)', {
-    userId,
-    message: userMessage.slice(0, 50),
-  });
-  return '__PASSTHROUGH__';
+  const startTime = Date.now();
+  logger.info('도메인 상담 시작', { userId, message: userMessage.substring(0, 100) });
+
+  try {
+    // 1. Check for existing session
+    let session = await getDomainSession(db, userId);
+
+    // 2. Create new session if none exists and message seems domain-related
+    //    (For first call, we always try to process - AI will return __PASSTHROUGH__ if not relevant)
+    if (!session) {
+      session = createDomainSession(userId, 'gathering');
+    }
+
+    // 3. Add user message to session
+    addMessageToSession(session, 'user', userMessage);
+
+    // 4. Call AI to get response and possible tool calls
+    const aiResult = await callDomainExpertAI(session, userMessage, env);
+
+    // 5. Handle __PASSTHROUGH__ - not domain related
+    if (aiResult.response === '__PASSTHROUGH__' || aiResult.response.includes('__PASSTHROUGH__')) {
+      logger.info('도메인 상담 패스스루', { userId });
+      // Don't save session if passthrough
+      return '__PASSTHROUGH__';
+    }
+
+    // 6. Execute tool calls if any
+    let toolResults: string[] = [];
+    if (aiResult.toolCalls && aiResult.toolCalls.length > 0) {
+      for (const toolCall of aiResult.toolCalls) {
+        const result = await executeDomainToolCall(
+          toolCall.name,
+          toolCall.arguments,
+          env,
+          userId,
+          db
+        );
+        toolResults.push(result);
+      }
+    }
+
+    // 7. Build final response
+    let finalResponse = aiResult.response;
+    if (toolResults.length > 0) {
+      // If we have tool results, include them in the response
+      // The AI response might be a summary, but tool results have the actual data
+      finalResponse = toolResults.join('\n\n');
+      if (aiResult.response && !aiResult.response.includes('__SESSION_END__')) {
+        finalResponse = aiResult.response + '\n\n' + finalResponse;
+      }
+    }
+
+    // 8. Handle __SESSION_END__ - session complete
+    if (finalResponse.includes('__SESSION_END__')) {
+      logger.info('도메인 상담 세션 종료', { userId });
+      await deleteDomainSession(db, userId);
+      finalResponse = finalResponse.replace('__SESSION_END__', '').trim();
+      return finalResponse;
+    }
+
+    // 9. Add assistant response to session and save
+    addMessageToSession(session, 'assistant', finalResponse);
+    session.updated_at = Date.now();
+    await saveDomainSession(db, session);
+
+    logger.info('도메인 상담 완료', {
+      userId,
+      duration: Date.now() - startTime,
+      hasToolCalls: aiResult.toolCalls?.length || 0
+    });
+
+    return finalResponse;
+
+  } catch (error) {
+    logger.error('도메인 상담 오류', error as Error, { userId });
+    return '죄송합니다. 도메인 상담 중 오류가 발생했습니다. 잠시 후 다시 시도해주세요.';
+  }
+}
+
+/**
+ * 도메인 세션 존재 여부 확인 (라우팅용)
+ *
+ * @param db - D1 Database
+ * @param userId - Telegram User ID
+ * @returns true if active session exists, false otherwise
+ */
+export async function hasDomainSession(db: D1Database, userId: string): Promise<boolean> {
+  const session = await getDomainSession(db, userId);
+  return session !== null && !isSessionExpired(session);
 }

src/tools/domain-tool.ts

@@ -470,7 +470,7 @@ async function callNamecheapApi(
 }
 
 // 도메인 작업 직접 실행 (Agent 없이 코드로 처리)
-async function executeDomainAction(
+export async function executeDomainAction(
   action: string,
   args: { domain?: string; nameservers?: string[]; tld?: string },
   allowedDomains: string[],