Fix PowerShell deploy stdin encoding

docs/CODEX_EXECUTION_LOG.md

@@ -3,6 +3,7 @@
 Changed:
 - Hardened `scripts/deploy_tower.sh` and `scripts/deploy_tower.ps1` so the remote Tower `.env` is sourced before building the all-in-one image.
 - Updated the PowerShell deploy wrapper to stream the remote script through `bash -s`, matching the Bash deploy path and preserving Bash variable expansion during `.env`-driven builds.
+- Forced UTF-8 without BOM for the PowerShell SSH stdin stream so the first remote Bash command is not prefixed with a BOM.
 - `GEOINTEL_INSTALL_AI=true` in `/mnt/user/appdata/geointel/.env` now drives the automatic image build by default; explicit local overrides remain possible for one-off deploys.
 - Documented the deploy behavior in `deploy/unraid/README.md`.
 
@@ -15,6 +16,7 @@ Tested:
 - `python -m pytest backend/tests/test_sprint31_unraid_template.py::test_tower_deploy_build_uses_remote_env_ai_setting_by_default backend/tests/test_sprint31_unraid_template.py::test_tower_deploy_uses_single_container_unraid_compose backend/tests/test_docker_runtime_config.py::test_unraid_deploy_passes_ai_build_arg_and_yolo_runtime_env` (`3 passed`).
 - Red step: `python -m pytest backend/tests/test_sprint31_unraid_template.py::test_powershell_tower_deploy_streams_remote_script_to_bash -q` failed because the PowerShell wrapper passed the remote script as an SSH command argument instead of streaming it to `bash -s`.
 - `python -m pytest backend/tests/test_sprint31_unraid_template.py::test_powershell_tower_deploy_streams_remote_script_to_bash backend/tests/test_sprint31_unraid_template.py::test_tower_deploy_build_uses_remote_env_ai_setting_by_default backend/tests/test_docker_runtime_config.py::test_unraid_deploy_passes_ai_build_arg_and_yolo_runtime_env -q` (`3 passed`).
+- Red step: the same PowerShell deploy transport test failed until the wrapper set `[System.Text.UTF8Encoding]::new($false)` for native-command stdin.
 
 ## Sprint 150 YOLO label visible-ratio gate (2026-07-09)