fix: add explicit UTF-8 encoding to all subprocess text=True calls (#53428)

On Windows with Chinese locale (GBK), subprocess.run(text=True) without
explicit encoding causes UnicodeDecodeError crashes. This fix adds
encoding='utf-8', errors='replace' to all subprocess.run() and
subprocess.Popen() calls that use text=True across 76 non-test Python files.

Fixes #53428 (master tracker for Windows GBK locale crash).

Note: credential_pool.py and electron changes excluded per reviewer request —
those will be submitted as separate focused PRs.

hermes_cli/copilot_auth.py

@@ -147,7 +147,7 @@ def _try_gh_cli_token() -> Optional[str]:
             result = subprocess.run(
                 cmd,
                 capture_output=True,
-                text=True,
+                text=True, encoding='utf-8', errors='replace',
                 timeout=5,
                 env=clean_env,
                 **_popen_kwargs,