feat: add --allow-file-access flag for file:// URL support (#375)

* feat: add --allow-file-access flag for file:// URL support

Adds the ability to open and interact with local files using file:// URLs.
This enables use cases like viewing local PDFs, testing local HTML files,
and allowing JavaScript to access other local files via XHR.

The flag adds Chromium's --allow-file-access-from-files and --allow-file-access
launch arguments. Only supported in Chromium browsers.

Fixes #345

* fix: add cli_allow_file_access tracking to prevent spurious warning

When --allow-file-access is set via AGENT_BROWSER_ALLOW_FILE_ACCESS env var
(not CLI), don't warn about the flag being ignored when daemon is already running.

src/daemon.ts

@@ -311,6 +311,7 @@ export async function startDaemon(options?: {
                 : undefined;
 
               const ignoreHTTPSErrors = process.env.AGENT_BROWSER_IGNORE_HTTPS_ERRORS === '1';
+              const allowFileAccess = process.env.AGENT_BROWSER_ALLOW_FILE_ACCESS === '1';
               await manager.launch({
                 id: 'auto',
                 action: 'launch' as const,
@@ -323,6 +324,7 @@ export async function startDaemon(options?: {
                 userAgent: process.env.AGENT_BROWSER_USER_AGENT,
                 proxy,
                 ignoreHTTPSErrors: ignoreHTTPSErrors,
+                allowFileAccess: allowFileAccess,
               });
             }
           }