feat: switch AI provider from Anthropic to DeepSeek

- lib/claude/client.ts: replace Anthropic SDK with openai package pointed at DeepSeek baseURL
- 4 AI routes: port tool definitions, tool_choice, and output parsing to OpenAI function-calling format
- Drop thinking:{type:'adaptive'} (no DeepSeek equivalent); model string → deepseek-chat
- settings/route.ts: add DEEPSEEK_API_KEY to ALLOWED_KEYS
- migration: seed DEEPSEEK_API_KEY placeholder row in app_settings
- tests: update 3 AI route tests to mock createDeepSeekClient + OpenAI response shape

Voyage AI embedding path untouched (DeepSeek has no embeddings endpoint).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CPf5Rc8QPx6V8KLEEgfKEQ

app/api/incidents/[id]/ai/rca-draft/route.ts

@@ -2,7 +2,7 @@ export const dynamic = 'force-dynamic'
 
 import { NextRequest, NextResponse } from 'next/server'
 import { createClient } from '@/lib/supabase/server'
-import { createAnthropicClient } from '@/lib/claude/client'
+import { createDeepSeekClient } from '@/lib/claude/client'
 import { getApiKey } from '@/lib/settings'
 
 export async function POST(
@@ -28,8 +28,8 @@ export async function POST(
   if ((recentCount ?? 0) > 0)
     return NextResponse.json({ error: 'Rate limited — please wait 60 seconds' }, { status: 429 })
 
-  const anthropicKey = await getApiKey(supabase, 'ANTHROPIC_API_KEY')
-  const anthropic = createAnthropicClient(anthropicKey)
+  const deepseekKey = await getApiKey(supabase, 'DEEPSEEK_API_KEY')
+  const client = createDeepSeekClient(deepseekKey)
 
   const { data: incident } = await supabase
     .from('incidents')
@@ -55,44 +55,46 @@ export async function POST(
   const siteName = (incident.sites as unknown as { name: string } | null)?.name ?? 'Unknown'
   const zoneName = (incident.zones as unknown as { name: string } | null)?.name ?? 'Unknown'
 
-  let message: Awaited<ReturnType<typeof anthropic.messages.create>>
+  let res: Awaited<ReturnType<typeof client.chat.completions.create>>
   try {
-    message = await anthropic.messages.create({
-      model: 'claude-opus-4-8',
-      thinking: { type: 'adaptive' },
+    res = await client.chat.completions.create({
+      model: 'deepseek-chat',
       max_tokens: 2048,
       tools: [{
-        name: 'draft_rca',
-        description: 'Draft a 5-Why root cause analysis and CAPA suggestions for an HSE incident',
-        input_schema: {
-          type: 'object' as const,
-          properties: {
-            five_why_steps: {
-              type: 'array',
-              items: {
-                type: 'object',
-                properties: {
-                  why: { type: 'string', description: 'The why question' },
-                  answer: { type: 'string', description: 'The finding or answer' },
+        type: 'function',
+        function: {
+          name: 'draft_rca',
+          description: 'Draft a 5-Why root cause analysis and CAPA suggestions for an HSE incident',
+          parameters: {
+            type: 'object',
+            properties: {
+              five_why_steps: {
+                type: 'array',
+                items: {
+                  type: 'object',
+                  properties: {
+                    why: { type: 'string', description: 'The why question' },
+                    answer: { type: 'string', description: 'The finding or answer' },
+                  },
+                  required: ['why', 'answer'],
                 },
-                required: ['why', 'answer'],
+                description: '3 to 5 why steps',
+              },
+              root_cause_summary: {
+                type: 'string',
+                description: 'One-sentence root cause statement',
+              },
+              capa_suggestions: {
+                type: 'array',
+                items: { type: 'string' },
+                description: 'Up to 3 corrective/preventive action suggestions',
               },
-              description: '3 to 5 why steps',
-            },
-            root_cause_summary: {
-              type: 'string',
-              description: 'One-sentence root cause statement',
-            },
-            capa_suggestions: {
-              type: 'array',
-              items: { type: 'string' },
-              description: 'Up to 3 corrective/preventive action suggestions',
             },
+            required: ['five_why_steps', 'root_cause_summary', 'capa_suggestions'],
           },
-          required: ['five_why_steps', 'root_cause_summary', 'capa_suggestions'],
         },
       }],
-      tool_choice: { type: 'tool', name: 'draft_rca' },
+      tool_choice: { type: 'function', function: { name: 'draft_rca' } },
       messages: [{
         role: 'user',
         content: `You are an experienced HSE investigator for a Malaysian 3PL warehouse. Draft a 5-Why root cause analysis for this incident.
@@ -114,15 +116,12 @@ Provide 3–5 Why steps drilling from immediate cause to root cause. Give a one-
     return NextResponse.json({ error: 'AI service unavailable' }, { status: 503 })
   }
 
-  const toolBlock = message.content.find(b => b.type === 'tool_use')
-  if (!toolBlock || toolBlock.type !== 'tool_use')
-    return NextResponse.json({ error: 'AI draft failed' }, { status: 500 })
+  const call = res.choices[0]?.message?.tool_calls?.[0]
+  if (!call || call.type !== 'function') return NextResponse.json({ error: 'AI draft failed' }, { status: 500 })
 
-  const draft = toolBlock.input as {
-    five_why_steps?: unknown
-    root_cause_summary?: unknown
-    capa_suggestions?: unknown
-  }
+  let draft: { five_why_steps?: unknown; root_cause_summary?: unknown; capa_suggestions?: unknown }
+  try { draft = JSON.parse(call.function.arguments) }
+  catch { return NextResponse.json({ error: 'AI returned unexpected structure' }, { status: 500 }) }
 
   if (
     !Array.isArray(draft.five_why_steps) ||
@@ -138,7 +137,7 @@ Provide 3–5 Why steps drilling from immediate cause to root cause. Give a one-
     p_action: 'ai_rca_draft',
     p_new_value: {
       root_cause_summary: draft.root_cause_summary,
-      model: 'claude-opus-4-8',
+      model: 'deepseek-chat',
     } as never,
   })