`pathlib.Path('~user').expanduser()` raises RuntimeError when the
tilde-expansion can't resolve the user (e.g. `~500-700` where the LLM
meant "approximately 500-700" rather than a path). The hint walker's
existing `except (OSError, ValueError):` clauses do not catch
RuntimeError, so it escapes through the tool dispatcher and surfaces
in the conversation loop as a misleading
Error during OpenAI-compatible API call #N:
Could not determine home directory.
Reproduced across three unrelated models (openai/gpt-5-mini,
openai/gpt-5.1-codex, deepseek/deepseek-v4-flash) on terminal-tool
commands containing literal tildes in non-path contexts — common in
LLM output ("~500 agencies", "~45,000 CVEs", "~80/hr blended rate").
Reproduction (one-liner):
>>> from pathlib import Path
>>> Path("~500-700").expanduser()
RuntimeError: Could not determine home directory.
Fix: extend the three `except` clauses in
agent/subdirectory_hints.py to also catch RuntimeError:
line 138 (_add_path_candidate's outer catch around the Path().expanduser() call)
lines 198+202 (_load_hints_for_directory's nested catches around hint_path.relative_to(Path.home()))
Tests: tests/agent/test_subdirectory_hints_tilde.py adds three cases
covering: tilde-as-approximately in heredoc commands, ~unknown_user paths,
and a regression guard that legitimate ~/path expansion still works.
