fix: guard os.getcwd() against deleted CWD (FileNotFoundError)

[lbruceolson]

What does this PR do?

Python's os.getcwd() raises FileNotFoundError when the shell's current working directory no longer exists on disk. This happens when a terminal (e.g. Warp) is open in a directory that gets deleted or renamed while the pane is still sitting in it. The result is hermes crashing before it can even display the banner.

This PR adds a _safe_getcwd() helper that wraps os.getcwd() in a try/except FileNotFoundError and falls back to the user's home directory (~). All six bare os.getcwd() call sites in cli.py are replaced with _safe_getcwd():

• load_cli_config() — initial CWD resolution
• • HermesCLI.show_banner() — banner display
• • HermesCLI checkpoint command handler
• • HermesCLI._show_config() — /config display
• • HermesCLI.run() tools-refresh path
• • preprocess_context_references() call — context file expansion

Related Issue

No existing issue. Discovered during normal use with the Warp terminal on Linux.

Type of Change

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

Reproducer

1. Open a terminal pane in any directory (e.g. /tmp/test-dir)
2. 2. Delete that directory from another shell: rm -rf /tmp/test-dir
3. 3. Launch hermes from the original pane
4. 4. Without this fix: FileNotFoundError: [Errno 2] No such file or directory
5. 5. With this fix: hermes starts normally, CWD falls back to ~

[alt-glitch]

Likely duplicate of #10233 — same os.getcwd() FileNotFoundError guard in CLI startup.

[alt-glitch]

Likely duplicate of #10233 — same os.getcwd() FileNotFoundError guard in CLI startup.

[teknium1]

Thanks for identifying a real deleted-CWD failure mode. The startup defect still exists on current main, but this patch needs current-tree salvage and broader launch-surface coverage.

Problems

• cli.py:602 still calls os.getcwd() unconditionally for the local backend in load_cli_config(), before the classic CLI can render its banner.
• The PR only changes cli.py; the TUI launcher independently calls os.getcwd() at hermes_cli/main.py:2037.
• Current cli.py:2855 also uses os.getenv("TERMINAL_CWD", os.getcwd()); the default expression is evaluated eagerly, so a deleted CWD still raises even when TERMINAL_CWD is set.
• The diff adds no regression test. Existing deleted-CWD tests cover only tools/terminal_tool.py (tests/tools/test_terminal_task_cwd.py:226-247).

Suggested changes

• Port the guard to the current load_cli_config() branch at cli.py:593-605 and add a test that makes cli.os.getcwd() raise while invoking the real loader.
• Cover the TUI launch path at hermes_cli/main.py:2037 and the remaining current CLI callers.

Automated hermes-sweeper review.

[teknium1]

Please extend this recovery to the TUI launcher as well: current hermes_cli/main.py:2037 independently calls os.getcwd() while setting HERMES_CWD, and this cli.py-only patch cannot protect that startup path.