feat(browser_eval): support 'chromium' browser (Linux arm64)

On platforms where the only available Chrome build is Chromium (e.g. Linux
arm64), the browser_eval tool couldn't be used because the browser enum
only accepted chrome/firefox/webkit/msedge.

@playwright/mcp accepts '--browser chromium' (it resolves to the
chrome-for-testing build). Verified end-to-end against @playwright/mcp@0.0.75:
started the server with '--browser chromium' and a browser_navigate call
launched and loaded a page successfully.

Add 'chromium' to the browser enum (tool input schema + arg type) and the
manager option type; it is forwarded as '--browser chromium'.

Fixes #123

Author: gaojude

src/_internal/browser-eval-manager.ts

@@ -48,7 +48,7 @@ export async function ensureBrowserEvalMCP(): Promise<void> {
  * Start playwright-mcp server and connect to it
  */
 export async function startBrowserEvalMCP(options?: {
-  browser?: "chrome" | "firefox" | "webkit" | "msedge"
+  browser?: "chrome" | "chromium" | "firefox" | "webkit" | "msedge"
   headless?: boolean
 }): Promise<MCPConnection> {
   // Ensure playwright-mcp is installed

src/tools/browser-eval.ts

@@ -25,9 +25,11 @@ export const inputSchema = {
     .describe("The action to perform using browser automation"),
 
   browser: z
-    .enum(["chrome", "firefox", "webkit", "msedge"])
+    .enum(["chrome", "chromium", "firefox", "webkit", "msedge"])
     .optional()
-    .describe("Browser to use (default: chrome). Only used with 'start' action."),
+    .describe(
+      "Browser to use (default: chrome). Use 'chromium' on platforms without a Chrome build (e.g. Linux arm64). Only used with 'start' action."
+    ),
   headless: z
     .union([z.boolean(), z.string().transform((val) => val === "true")])
     .optional()
@@ -129,7 +131,7 @@ type BrowserEvalArgs = {
     | "drag"
     | "upload_file"
     | "list_tools"
-  browser?: "chrome" | "firefox" | "webkit" | "msedge"
+  browser?: "chrome" | "chromium" | "firefox" | "webkit" | "msedge"
   headless?: boolean | string
   url?: string
   element?: string