fix(terminal): guard os.getcwd() against deleted CWD in _get_env_config

[liuhao1024]

What does this PR do?

_get_env_config() calls os.getcwd() unconditionally for the local backend. When the process's current working directory has been deleted (common on Arch Linux where /tmp is tmpfs and stale namespaces are reaped aggressively), this raises FileNotFoundError.

The cleanup thread calls _get_env_config() every 60 seconds. Although the exception is caught by the thread's except Exception handler, it logs a full traceback to errors.log on every tick — creating a recurring, noisy warning that never resolves.

Related Issue

Fixes #33367

Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)

Changes Made

• tools/terminal_tool.py: Guard os.getcwd() against deleted CWD
• tests/tools/test_terminal_cleanup_cwd.py: Regression tests for FileNotFoundError and OSError

How to Test

1. Run pytest tests/ -q — all tests should pass
2. Verify the specific scenario described above is resolved

Checklist

Code

• I've read the Contributing Guide
• My commit messages follow Conventional Commits (fix(scope):, feat(scope):, etc.)
• I searched for existing PRs to make sure this isn't a duplicate
• My PR contains only changes related to this fix/feature (no unrelated commits)
• I've run pytest tests/ -q and all tests pass
• I've added tests for my changes (required for bug fixes, strongly encouraged for features)
• I've tested on my platform: macOS 26.4.1

Documentation & Housekeeping

• I've updated relevant documentation (README, docs/, docstrings) — or N/A
• I've updated cli-config.yaml.example if I added/changed config keys — or N/A
• I've updated CONTRIBUTING.md or AGENTS.md if I changed architecture and workflows — or N/A
• I've considered cross-platform impact (Windows, macOS) per the compatibility guide — or N/A

Code Intelligence

• Analyzed: Function:tools/terminal_tool.py:_get_env_config (callers: 10+ including terminal_tool, file_tools, code_execution_tool, cleanup_thread_worker, prompt_builder)
• Blast radius: LOW — single line change with safe fallback; all callers benefit from the guard
• Related patterns: os.getcwd() is also called at line 978 (docker CWD passthrough) but only when env_type == "docker", which is not the affected code path

[alt-glitch]

Related to open #4982 and #10233 (same os.getcwd() guard for cli.py), and merged #19933 (same guard for process_registry.py). This PR targets a different call site (tools/terminal_tool.py:_get_env_config) — complementary fix, not a duplicate.

[teknium1]

Thanks for the focused report and regression coverage. This is now implemented on main.

• Automated hermes-sweeper review verified tools/terminal_tool.py:1196–1207: _safe_getcwd() handles a deleted CWD and falls back to TERMINAL_CWD or the home directory.
• _get_env_config() uses that helper for the local backend at tools/terminal_tool.py:1294.
• Regression coverage is present at tests/tools/test_terminal_task_cwd.py:231–247.
• The implementation landed in ad69d3edc7359310233fa789b300bfcc5a5c3f7a and is included in v2026.6.5.

The current implementation also routes the Docker cwd-passthrough and debug-config call sites through the same helper.