fix(git): never block internal git calls on credential prompts

Port from openai/codex#34540 / #34612 ("detach non-interactive
subprocesses from stdin"): internal git invocations that run with nobody
attached — MCP catalog installs, plugin install/update, profile
distribution staging, worktree base fetches, and the desktop review
pane's git/gh backend — could hang on a credential prompt when a remote
is private, misconfigured, or requires auth. git prompts on the
inherited terminal (or via Git Credential Manager on Windows), so the
operation silently waits until its timeout, or forever at sites without
one (mcp_catalog clones have no timeout at all and inherit the parent
terminal).

- Add noninteractive_git_env() to hermes_cli/_subprocess_compat.py:
  GIT_TERMINAL_PROMPT=0 + GCM_INTERACTIVE=Never on a copy of the
  environment; GIT_ASKPASS/SSH_ASKPASS deliberately preserved so
  working non-interactive auth still succeeds.
- Wire it + stdin=DEVNULL into: mcp_catalog._do_git_install (clone/
  checkout), plugins_cmd (clone + pull), profile_distribution._git_clone,
  web_git._git/_gh (gh also gets GH_PROMPT_DISABLED=1), and cli.py's
  worktree base fetch helper.
- Tests: env contract, a real-git E2E against a local 401 Basic-auth
  HTTP server proving fail-fast ("terminal prompts disabled") instead
  of a hang, and per-call-site plumbing assertions. Sabotage-verified:
  removing the env from web_git._git fails the site test.

hermes_cli/plugins_cmd.py

@@ -21,6 +21,7 @@ from pathlib import Path
 from typing import Any, Optional
 
 from hermes_constants import get_hermes_home
+from hermes_cli._subprocess_compat import noninteractive_git_env
 from hermes_cli.config import cfg_get
 from hermes_cli.secret_prompt import masked_secret_prompt
 
@@ -474,6 +475,8 @@ def _install_plugin_core(identifier: str, *, force: bool) -> tuple[Path, dict, s
                 capture_output=True,
                 text=True, encoding='utf-8', errors='replace',
                 timeout=60,
+                stdin=subprocess.DEVNULL,
+                env=noninteractive_git_env(),
             )
         except FileNotFoundError as e:
             raise PluginOperationError(
@@ -2005,6 +2008,8 @@ def _git_pull_plugin_dir(target: Path) -> tuple[bool, str]:
             text=True, encoding='utf-8', errors='replace',
             timeout=60,
             cwd=str(target),
+            stdin=subprocess.DEVNULL,
+            env=noninteractive_git_env(),
         )
     except FileNotFoundError:
         return False, "git is not installed or not in PATH."