fix(config): write config.yaml as UTF-8 to stop emoji/personality corruption (#51676)

atomic_yaml_write (and two sibling config writers) called yaml.dump
without allow_unicode=True. The default personalities shipped in cli.py
contain emoji/kaomoji, so PyYAML escaped astral-plane chars as 8-digit
\\UXXXXXXXX sequences inside multi-line double-quoted strings wrapped
with \\ line-continuations. Stricter/non-PyYAML parsers, editors, and
hand-edits break that structure into unclosed quotes, failing the whole
config parse -> silent fallback to defaults -> custom_providers lost.

Add allow_unicode=True to the canonical writer plus tui_gateway/server.py
and the telegram adapter's atomic config write so config is written as
readable UTF-8 with no escape/fold artifacts.

Fixes #51356

plugins/platforms/telegram/adapter.py

@@ -2030,7 +2030,13 @@ class TelegramAdapter(BasePlatformAdapter):
                 )
                 try:
                     with os.fdopen(fd, "w", encoding="utf-8") as f:
-                        _yaml.dump(config, f, default_flow_style=False, sort_keys=False)
+                        _yaml.dump(
+                            config,
+                            f,
+                            default_flow_style=False,
+                            sort_keys=False,
+                            allow_unicode=True,
+                        )
                         f.flush()
                         os.fsync(f.fileno())
                     atomic_replace(tmp_path, config_path)