feat(ai-client): multi-provider compat — native Anthropic/Google + URL tolerance

- TEXT/VISION: add native Anthropic & Google Gemini paths via Vercel AI SDK,
  selectable through TEXT_PROVIDER / VISION_PROVIDER (default openai_compatible)
- IMAGE: expand to openai (gpt-image) / google (Nano Banana) via AI SDK
  alongside the existing Runware task-array and OpenAI-compatible REST paths
- normalizeBaseUrl: tolerate URLs with/without /v1 (or /chat/completions);
  append the per-protocol version segment only for bare hosts
- config: readProvider() reads *_PROVIDER; types: ProviderProtocol + provider?
- deps: @ai-sdk/anthropic, @ai-sdk/google; docs in .env.example + README

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

lib/ai-client/chat.ts

@@ -1,5 +1,10 @@
-import type { ProviderConfig } from "@infiplot/types";
+import { generateText } from "ai";
+import type { LanguageModelUsage, ModelMessage } from "ai";
+import { createAnthropic } from "@ai-sdk/anthropic";
+import { createGoogleGenerativeAI } from "@ai-sdk/google";
+import type { ProviderConfig, ProviderProtocol } from "@infiplot/types";
 import { fetchWithRetry } from "./fetchWithRetry";
+import { normalizeBaseUrl } from "./normalizeUrl";
 
 export type ChatMessage = {
   role: "system" | "user" | "assistant";
@@ -57,6 +62,31 @@ function summarizeUsage(tag: string, usage: Usage | undefined): string {
   return `[cache] ${tag} prompt=${prompt} completion=${completion} (provider didn't report cache stats)`;
 }
 
+// AI SDK 6 unifies cache stats across providers into usage.inputTokenDetails,
+// so a single shape covers Anthropic + Gemini (no per-provider probing).
+function summarizeSdkUsage(
+  tag: string,
+  usage: LanguageModelUsage | undefined,
+): string {
+  if (!usage) return `[cache] ${tag} no-usage`;
+  const input = usage.inputTokens ?? 0;
+  const output = usage.outputTokens ?? 0;
+  const read = usage.inputTokenDetails?.cacheReadTokens;
+  const write = usage.inputTokenDetails?.cacheWriteTokens;
+  if (typeof read === "number" || typeof write === "number") {
+    const hit = read ?? 0;
+    const create = write ?? 0;
+    const rate = input > 0 ? ((hit / input) * 100).toFixed(1) : "n/a";
+    return `[cache] ${tag} hit=${hit} create=${create} input=${input} rate=${rate}% completion=${output}`;
+  }
+  return `[cache] ${tag} input=${input} completion=${output} (provider didn't report cache stats)`;
+}
+
+// text/vision default to the OpenAI-compatible wire protocol when unset.
+function resolveTextProtocol(config: ProviderConfig): ProviderProtocol {
+  return config.provider ?? "openai_compatible";
+}
+
 export async function chat(
   config: ProviderConfig,
   messages: ChatMessage[],
@@ -66,7 +96,63 @@ export async function chat(
     tag?: string;
   },
 ): Promise<string> {
-  const url = `${config.baseUrl.replace(/\/$/, "")}/chat/completions`;
+  const protocol = resolveTextProtocol(config);
+  if (protocol === "anthropic" || protocol === "google") {
+    return chatViaAiSdk(config, messages, opts, protocol);
+  }
+  return chatOpenAiCompatible(config, messages, opts);
+}
+
+// Native Anthropic / Gemini via the Vercel AI SDK. response_format is not sent
+// (Anthropic has no JSON mode); the engine relies on parseJsonLoose downstream,
+// matching how it already tolerates loose JSON from every provider.
+async function chatViaAiSdk(
+  config: ProviderConfig,
+  messages: ChatMessage[],
+  opts: { temperature?: number; tag?: string } | undefined,
+  protocol: "anthropic" | "google",
+): Promise<string> {
+  const baseURL = normalizeBaseUrl(config.baseUrl, protocol);
+  const model =
+    protocol === "anthropic"
+      ? createAnthropic({ apiKey: config.apiKey, baseURL })(config.model)
+      : createGoogleGenerativeAI({ apiKey: config.apiKey, baseURL })(
+          config.model,
+        );
+
+  const system = messages.find((m) => m.role === "system")?.content;
+  const convo: ModelMessage[] = messages
+    .filter((m) => m.role !== "system")
+    .map((m) => ({
+      role: m.role as "user" | "assistant",
+      content: m.content,
+    }));
+
+  const { text, usage } = await generateText({
+    model,
+    system,
+    messages: convo,
+    temperature: opts?.temperature ?? 0.9,
+  });
+
+  console.log(summarizeSdkUsage(opts?.tag ?? "chat", usage));
+
+  if (typeof text !== "string" || text.length === 0) {
+    throw new Error(`Chat API (AI SDK ${protocol}) returned no content.`);
+  }
+  return text;
+}
+
+async function chatOpenAiCompatible(
+  config: ProviderConfig,
+  messages: ChatMessage[],
+  opts?: {
+    temperature?: number;
+    responseFormat?: "json_object" | "text";
+    tag?: string;
+  },
+): Promise<string> {
+  const url = `${normalizeBaseUrl(config.baseUrl, "openai_compatible")}/chat/completions`;
   const body: Record<string, unknown> = {
     model: config.model,
     messages,