feat: streaming AI chat endpoint with tool calling

- POST /api/ai/stream: streamText with tools, streams response via toTextStreamResponse
- Tools: lookup_patient, lookup_appointments, lookup_doctor (same as existing chat endpoint)
- Uses stopWhen(stepCountIs(5)) for multi-step tool execution
- Streams response body to Express response manually (NestJS + AI SDK v6 compatibility)

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

src/ai/ai-chat.controller.ts

@@ -1,6 +1,7 @@
-import { Controller, Post, Body, Headers, HttpException, Logger } from '@nestjs/common';
+import { Controller, Post, Body, Headers, Req, Res, HttpException, Logger } from '@nestjs/common';
 import { ConfigService } from '@nestjs/config';
-import { generateText, tool, stepCountIs } from 'ai';
+import type { Request, Response } from 'express';
+import { generateText, streamText, tool, stepCountIs } from 'ai';
 import type { LanguageModel } from 'ai';
 import { z } from 'zod';
 import { PlatformGraphqlService } from '../platform/platform-graphql.service';
@@ -61,6 +62,129 @@ export class AiChatController {
         }
     }
 
+    @Post('stream')
+    async stream(@Req() req: Request, @Res() res: Response, @Headers('authorization') auth: string) {
+        if (!auth) throw new HttpException('Authorization required', 401);
+
+        const body = req.body;
+        const messages = body.messages ?? [];
+        if (!messages.length) throw new HttpException('messages required', 400);
+
+        if (!this.aiModel) {
+            res.status(500).json({ error: 'AI not configured' });
+            return;
+        }
+
+        const kb = await this.buildKnowledgeBase(auth);
+        const systemPrompt = this.buildSystemPrompt(kb);
+        const platformService = this.platform;
+
+        const result = streamText({
+            model: this.aiModel,
+            system: systemPrompt,
+            messages,
+            stopWhen: stepCountIs(5),
+            tools: {
+                lookup_patient: tool({
+                    description: 'Search for a patient/lead by phone number or name. Returns their profile, lead status, AI summary.',
+                    inputSchema: z.object({
+                        phone: z.string().optional().describe('Phone number to search'),
+                        name: z.string().optional().describe('Patient/lead name to search'),
+                    }),
+                    execute: async ({ phone, name }) => {
+                        const data = await platformService.queryWithAuth<any>(
+                            `{ leads(first: 50) { edges { node {
+                                id name contactName { firstName lastName }
+                                contactPhone { primaryPhoneNumber }
+                                source status interestedService
+                                contactAttempts lastContacted
+                                aiSummary aiSuggestedAction patientId
+                            } } } }`,
+                            undefined, auth,
+                        );
+                        const leads = data.leads.edges.map((e: any) => e.node);
+                        const phoneClean = (phone ?? '').replace(/\D/g, '');
+                        const nameClean = (name ?? '').toLowerCase();
+
+                        const matched = leads.filter((l: any) => {
+                            if (phoneClean) {
+                                const lp = (l.contactPhone?.primaryPhoneNumber ?? '').replace(/\D/g, '');
+                                if (lp.endsWith(phoneClean) || phoneClean.endsWith(lp)) return true;
+                            }
+                            if (nameClean) {
+                                const fn = `${l.contactName?.firstName ?? ''} ${l.contactName?.lastName ?? ''}`.toLowerCase();
+                                if (fn.includes(nameClean)) return true;
+                            }
+                            return false;
+                        });
+
+                        if (!matched.length) return { found: false, message: 'No patient/lead found.' };
+                        return { found: true, count: matched.length, leads: matched };
+                    },
+                }),
+
+                lookup_appointments: tool({
+                    description: 'Get appointments for a patient. Returns doctor, department, date, status.',
+                    inputSchema: z.object({
+                        patientId: z.string().describe('Patient ID'),
+                    }),
+                    execute: async ({ patientId }) => {
+                        const data = await platformService.queryWithAuth<any>(
+                            `{ appointments(first: 20, filter: { patientId: { eq: "${patientId}" } }, orderBy: [{ scheduledAt: DescNullsLast }]) { edges { node {
+                                id scheduledAt status doctorName department reasonForVisit
+                            } } } }`,
+                            undefined, auth,
+                        );
+                        return { appointments: data.appointments.edges.map((e: any) => e.node) };
+                    },
+                }),
+
+                lookup_doctor: tool({
+                    description: 'Get doctor details — schedule, clinic, fees, specialty.',
+                    inputSchema: z.object({
+                        doctorName: z.string().describe('Doctor name'),
+                    }),
+                    execute: async ({ doctorName }) => {
+                        const data = await platformService.queryWithAuth<any>(
+                            `{ doctors(first: 10) { edges { node {
+                                id fullName { firstName lastName }
+                                department specialty visitingHours
+                                consultationFeeNew { amountMicros currencyCode }
+                                clinic { clinicName }
+                            } } } }`,
+                            undefined, auth,
+                        );
+                        const doctors = data.doctors.edges.map((e: any) => e.node);
+                        const search = doctorName.toLowerCase();
+                        const matched = doctors.filter((d: any) => {
+                            const full = `${d.fullName?.firstName ?? ''} ${d.fullName?.lastName ?? ''}`.toLowerCase();
+                            return full.includes(search);
+                        });
+                        if (!matched.length) return { found: false, message: `No doctor matching "${doctorName}"` };
+                        return { found: true, doctors: matched };
+                    },
+                }),
+            },
+        });
+
+        const response = result.toTextStreamResponse();
+        res.status(response.status);
+        response.headers.forEach((value, key) => res.setHeader(key, value));
+        if (response.body) {
+            const reader = response.body.getReader();
+            const pump = async () => {
+                while (true) {
+                    const { done, value } = await reader.read();
+                    if (done) { res.end(); break; }
+                    res.write(value);
+                }
+            };
+            pump().catch(() => res.end());
+        } else {
+            res.end();
+        }
+    }
+
     private async buildKnowledgeBase(auth: string): Promise<string> {
         const now = Date.now();
         if (this.knowledgeBase && now - this.kbLoadedAt < this.kbTtlMs) {