fix(windows): hide console-window flash on gateway-runtime subprocess spawns

[AIalliAI]

Summary

On Windows, when the gateway runs without a console (Desktop app / background service), every console child process it spawns opens a visible conhost window that flickers and steals focus — the behavior reported in #43848.

The main terminal-tool execution path already hides its window via windows_hide_flags() (tools/environments/local.py), and the same convention exists in tools/process_registry.py and cron/scheduler.py — but a number of spawn sites reachable during a normal agent turn were missed. The most user-visible ones run on every message (git workspace probes during prompt building) or on every file edit (checkpoint git calls), which is what makes the flicker so noticeable.

Change

Pass creationflags=windows_hide_flags() (CREATE_NO_WINDOW; returns 0 on POSIX, so non-Windows behavior is unchanged) at the gateway-runtime spawn sites:

Per agent turn

• agent/coding_context.py — git workspace probes during prompt building (several per message)
• agent/context_references.py — @git/@diff reference git calls and rg --files listing
• tools/checkpoint_manager.py — shadow-store git calls on every checkpointed file edit
• agent/shell_hooks.py — user-configured hook commands
• agent/skill_preprocessing.py — SKILL.md inline-shell snippets

Terminal tool probes (first commit)

• tools/terminal_tool.py — sudo -n true probe (Windows 11 ships a sudo), docker version / apptainer --version backend probes

Process cleanup (taskkill tree-kills, Windows-only branches)

• gateway/status.py::terminate_pid, tools/tts_tool.py, tools/transcription_tools.py

Runtime installs / probes

• tools/lazy_deps.py — uv pip / pip / ensurepip runtime dependency installs (these otherwise show a console window for the whole install)
• tools/env_probe.py — interpreter/binary version probes

Container/remote backends

• tools/environments/base.py — _popen_bash now defaults creationflags to windows_hide_flags() (via setdefault, so callers can still override), covering the shared docker exec / ssh per-command spawn path
• tools/environments/docker.py — container lifecycle and probe spawns (docker ps/rm/inspect/run/start/stop/info/create)
• tools/environments/ssh.py — control-master setup, scp/tar sync, and remote command spawns

Sites intentionally left alone: macOS-only spawns (security, scutil), interactive flows that must keep the console (claude setup-token), and the interactive CLI (a console already exists there, so nothing flashes).

Testing

• New regression tests in tests/tools/test_windows_native_support.py (TestGatewayRuntimeSpawnsHideConsole) simulate Windows by flipping IS_WINDOWS in _subprocess_compat and assert the CREATE_NO_WINDOW bit reaches subprocess.run for the per-turn probes, taskkill paths, and inline-shell helper. Verified they fail against unpatched modules.
• Existing suites for all touched modules pass: 348 tests across test_coding_context, test_context_references, test_shell_hooks, test_checkpoint_manager, test_env_probe, test_lazy_deps, test_windows_native_support, test_status, plus the terminal-tool suites (220 more).

Fixes #43848

[AIalliAI]

Pushed a second commit expanding this beyond the terminal-tool probes: the dominant flicker sources on the default local backend turn out to be the spawns that run on every agent message — the git workspace probes in agent/coding_context.py (prompt building), the checkpoint git calls in tools/checkpoint_manager.py (every file edit), and @git/@diff context references — plus the taskkill tree-kills and runtime pip/uv installs. All now pass creationflags=windows_hide_flags() following the existing convention. Added regression tests (TestGatewayRuntimeSpawnsHideConsole) that simulate Windows and assert the CREATE_NO_WINDOW bit reaches subprocess.run. PR description updated with the full site list.

[AIalliAI]

Requesting maintainer review — this is ready to land from my side. Just merge-synced with current main (the only conflict was a trivial AUTHOR_MAP keep-both in scripts/release.py); the PR's touched test files pass locally on the merged head. Standalone fork CI is pending first-run approval here; the rollup branch in #44061 carrying this session's batch is fully green on upstream CI.

[AIalliAI]

Superseded: the CREATE_NO_WINDOW/DETACHED_PROCESS fix reached main via hermes_cli._subprocess_compat module. Different implementation, same outcome.