Fix key mapping in Anthropic CUA Client (#1374)

# why
Anthropic agents in CUA mode are unable to issue key presses (not to be
confused with `type` actions)

# what changed
The format for the anthropic tool `computer_20250124` replies with:
```ts
{
  "action":"key",
  "text":"BackSpace"
}
```
wasn't properly mapped to our internal action abstraction: `keypress`,
which accepts parameter `keys`. It was issued directly from the
anthropic format. Updated `AnthropicCUAClient.ts` to account for this
and map appropriately

# test plan
- [x] Tested on sample eval






<!-- This is an auto-generated description by cubic. -->
---
## Summary by cubic
Fixes key action mapping in Anthropic CUA so agents can send key presses
(e.g., Backspace) correctly instead of failing on the "key" action.

- **Bug Fixes**
- Map Anthropic "key" to internal "keypress" and pass keys from
input.text.
- Remove the old "key" path and Playwright key mapping to avoid
mismatches.

<sup>Written for commit b9716b9.
Summary will update automatically on new commits.</sup>

<!-- End of auto-generated description by cubic. -->

---------

Co-authored-by: Sean McGuire <75873287+seanmcguire12@users.noreply.github.com>
Co-authored-by: greptile-apps[bot] <165735046+greptile-apps[bot]@users.noreply.github.com>

Author: 3 people

.changeset/shy-sides-crash.md

@@ -0,0 +1,5 @@
+---
+"@browserbasehq/stagehand": patch
+---
+
+Fix key action mapping in Anthropic CUA

packages/core/lib/v3/agent/AnthropicCUAClient.ts

@@ -15,7 +15,6 @@ import { AgentScreenshotProviderError } from "../types/public/sdkErrors";
 import Anthropic from "@anthropic-ai/sdk";
 import { ToolSet } from "ai";
 import { AgentClient } from "./AgentClient";
-import { mapKeyToPlaywright } from "./utils/cuaKeyMapping";
 import { compressConversationImages } from "./utils/imageCompression";
 import { toJsonSchema } from "../zodCompat";
 import type { StagehandZodSchema } from "../zodCompat";
@@ -772,10 +771,10 @@ export class AnthropicCUAClient extends AgentClient {
             text: input.text as string,
             ...input,
           };
-        } else if (action === "keypress") {
+        } else if (action === "keypress" || action === "key") {
           return {
             type: "keypress",
-            keys: input.keys as string[],
+            keys: [input.text as string],
             ...input,
           };
         } else if (action === "double_click" || action === "doubleClick") {
@@ -865,15 +864,6 @@ export class AnthropicCUAClient extends AgentClient {
             type: "wait",
             ...input,
           };
-        } else if (action === "key") {
-          const text = input.text as string;
-          const mappedKey = mapKeyToPlaywright(text);
-
-          return {
-            type: "key",
-            text: mappedKey,
-            ...input,
-          };
         } else if (action === "left_click") {
           // Convert left_click to regular click
           const coordinates = input.coordinate as number[] | undefined;