feat(ai): Add Amazon Bedrock provider (#494)

Adds support for Amazon Bedrock with Claude models including:
- Full streaming support via Converse API
- Reasoning/thinking support for Claude models
- Cross-region inference model ID handling
- Multiple AWS credential sources (profile, IAM keys, API keys)
- Image support in messages and tool results
- Unicode surrogate sanitization

Also adds 'Adding a New Provider' documentation to AGENTS.md and README.

Co-authored-by: nickchan2 <nickchan2@users.noreply.github.com>

packages/agent/test/e2e.test.ts

@@ -2,6 +2,7 @@ import type { AssistantMessage, Model, ToolResultMessage, UserMessage } from "@m
 import { getModel } from "@mariozechner/pi-ai";
 import { describe, expect, it } from "vitest";
 import { Agent } from "../src/index.js";
+import { hasBedrockCredentials } from "./bedrock-utils.js";
 import { calculateTool } from "./utils/calculate.js";
 
 async function basicPrompt(model: Model<any>) {
@@ -324,6 +325,30 @@ describe("Agent E2E Tests", () => {
 			await multiTurnConversation(model);
 		});
 	});
+
+	describe.skipIf(!hasBedrockCredentials())("Amazon Bedrock Provider (claude-sonnet-4-5)", () => {
+		const model = getModel("amazon-bedrock", "global.anthropic.claude-sonnet-4-5-20250929-v1:0");
+
+		it("should handle basic text prompt", async () => {
+			await basicPrompt(model);
+		});
+
+		it("should execute tools correctly", async () => {
+			await toolExecution(model);
+		});
+
+		it("should handle abort during execution", async () => {
+			await abortExecution(model);
+		});
+
+		it("should emit state updates during streaming", async () => {
+			await stateUpdates(model);
+		});
+
+		it("should maintain context across multiple turns", async () => {
+			await multiTurnConversation(model);
+		});
+	});
 });
 
 describe("Agent.continue()", () => {