fonts: stop injecting STEALTHFOX_FONTLIST/SYSTEMUI env (binary self-contained)

The patched binary is always bundle-only and needs no external font config, so
the wrapper no longer injects any font env in _build_env (sync + async). No
external font customization channel remains. Test updated.

src/invisible_playwright/async_api.py

@@ -227,16 +227,8 @@ class InvisiblePlaywright:
         env = _os.environ.copy()
         if self._timezone:
             env["TZ"] = _tz_env(self._timezone)
-        # Font allow-list + system-ui via env (read at the gfxPlatformFontList
-        # constructor, process start) — Playwright delivers firefox_user_prefs
-        # over the juggler protocol after start, too late for the font list ctor,
-        # so without this host fonts leak on Linux/macOS. See sync launcher.
-        fontlist = prefs.get("zoom.stealth.font.fontlist")
-        if fontlist:
-            env["STEALTHFOX_FONTLIST"] = fontlist
-        system_ui = prefs.get("zoom.stealth.font.system_ui")
-        if system_ui:
-            env["STEALTHFOX_SYSTEMUI"] = system_ui
+        # Fonts need NO env: the patched binary is self-contained (always
+        # bundle-only). No external font list / allow-list / system-ui.
         # WebRTC srflx override: feed nICEr's nr_stealth_bridge the proxy egress
         # IP (caller's explicit env var wins, else the IP auto-discovered in
         # __aenter__) and drop IPv6 from gathering behind a proxy.

src/invisible_playwright/launcher.py

@@ -382,24 +382,14 @@ class InvisiblePlaywright:
         a synthetic srflx candidate matching the proxy egress IP, avoiding
         the StaticPref IPC propagation timing issue between parent and
         socket processes.
-        ``STEALTHFOX_FONTLIST`` / ``STEALTHFOX_SYSTEMUI`` carry the font
-        allow-list + system-ui family for the SAME reason: the binary reads
-        them at the gfxPlatformFontList constructor (process start), but
-        Playwright delivers firefox_user_prefs over the juggler protocol
-        AFTER start — too late for the font list ctor. The env var is present
-        at start and inherited by content processes, so the allow-list is
-        applied on every host (without it, host fonts leak on Linux/macOS).
+        Fonts need NO env: the patched binary is self-contained (always
+        bundle-only, exposing exactly the bundled standard-Windows families;
+        system-ui + generics baked in C++). No external font list / allow-list.
         """
         import os as _os
         env = _os.environ.copy()
         if self._timezone:
             env["TZ"] = _tz_env(self._timezone)
-        fontlist = prefs.get("zoom.stealth.font.fontlist")
-        if fontlist:
-            env["STEALTHFOX_FONTLIST"] = fontlist
-        system_ui = prefs.get("zoom.stealth.font.system_ui")
-        if system_ui:
-            env["STEALTHFOX_SYSTEMUI"] = system_ui
         # WebRTC srflx override: feed nICEr's nr_stealth_bridge the proxy egress
         # IP so the srflx candidate matches the proxy (not the real host the
         # UDP STUN would otherwise leak). An explicit env var set by the caller

tests/test_launcher_helpers.py

@@ -207,18 +207,18 @@ def test_build_env_caller_env_override_wins(monkeypatch):
 
 
 @pytest.mark.unit
-def test_build_env_injects_font_list_and_system_ui():
-    # The binary reads these at the gfxPlatformFontList constructor (process
-    # start); Playwright delivers firefox_user_prefs over juggler AFTER start, so
-    # the env var is the only at-construction channel. Without it host fonts leak
-    # on Linux/macOS (the wrapper's pref-only delivery was a cross-OS gap).
+def test_build_env_never_injects_font_env():
+    # The patched binary is self-contained for fonts (always bundle-only; the
+    # exposed set IS the bundle, system-ui + generics baked in C++). The wrapper
+    # must NOT inject any STEALTHFOX_FONTLIST/SYSTEMUI env — even if legacy font
+    # prefs are passed — so there is no external font customization channel.
     ip = InvisiblePlaywright(seed=42)
     env = ip._build_env({
         "zoom.stealth.font.fontlist": "arial,calibri,segoe ui",
         "zoom.stealth.font.system_ui": "Segoe UI",
     })
-    assert env["STEALTHFOX_FONTLIST"] == "arial,calibri,segoe ui"
-    assert env["STEALTHFOX_SYSTEMUI"] == "Segoe UI"
+    assert "STEALTHFOX_FONTLIST" not in env
+    assert "STEALTHFOX_SYSTEMUI" not in env
 
 
 @pytest.mark.unit