chore(conformance): bump @xterm/headless to 6.1.0-beta.199

Pinned version advanced from 6.1.0-beta.195 (gitHead 1432e200) to
6.1.0-beta.199 (gitHead 09116882). Diff across all files listed in
PORTING_SPEC.md File Mapping is empty — upstream commits in range touch
only non-ported files (KittyKeyboard browser encoder, TaskQueue
idle-callback shim, test utilities).

Regenerated conformance/testdata/golden.json: no changes (confirming
no behavioral drift in ported surface). Full test suite passes.

Fixes #17

Co-authored-by: Ona <no-reply@ona.com>

Author: ona-automations

conformance/package.json

@@ -6,6 +6,6 @@
     "generate": "node generate.mjs"
   },
   "dependencies": {
-    "@xterm/headless": "6.1.0-beta.195"
+    "@xterm/headless": "6.1.0-beta.199"
   }
 }

conformance/yarn.lock

@@ -2,7 +2,7 @@
 # yarn lockfile v1
 
 
-"@xterm/headless@6.1.0-beta.195":
-  version "6.1.0-beta.195"
-  resolved "https://registry.yarnpkg.com/@xterm/headless/-/headless-6.1.0-beta.195.tgz#a83df9a8c4bfe740a36461e5f3b9fd04256d4455"
-  integrity sha512-sUOeZ08431n5wx6ukrQ96eXEGN7z8swUfvHkl4nAEqpYEMxS/ua+E6v5PGT6fpQFbOt2R3zIm6LDIfy9GX24mA==
+"@xterm/headless@6.1.0-beta.199":
+  version "6.1.0-beta.199"
+  resolved "https://registry.yarnpkg.com/@xterm/headless/-/headless-6.1.0-beta.199.tgz#cc5ea68420011dba5decb73dbd04c6a9fdea167a"
+  integrity sha512-7p1FEXBXBYeXySmoe7Mpta+XBrFcuBD/j9gNuM5SttWgGAh3InXYZgWbhrNTZE712CglfSOolmd0LzpQUnP5+g==