fix(prompt): honor TERMINAL_CWD in local environment hints

[ArnBdev]

Summary

Use TERMINAL_CWD when building local environment hints so the prompt reports the same current working directory that the terminal tool will use by default.

If TERMINAL_CWD is not set, the existing os.getcwd() behavior is preserved.

Why

Long-running Hermes processes can be launched from one directory while a session, cron job, worktree, or worker is configured to run terminal commands from another directory.

In that case, the terminal tool may correctly default to TERMINAL_CWD, but the prompt still reports the process cwd from os.getcwd(). This can mislead the model into passing the stale prompt cwd back as an explicit workdir, overriding the intended terminal default.

Changes

• Prefer TERMINAL_CWD over os.getcwd() in build_environment_hints().
• Expand ~ in the reported cwd for consistency.
• Add a regression test covering local-backend environment hints with TERMINAL_CWD.

Test plan

python -m pytest tests/agent/test_prompt_builder.py::TestEnvironmentHints::test_build_environment_hints_uses_terminal_cwd_for_local_backend -q -o 'addopts='

Also run together with the related delegate timeout diagnostic tests:

python -m pytest \
  tests/agent/test_prompt_builder.py::TestEnvironmentHints::test_build_environment_hints_uses_terminal_cwd_for_local_backend \
  tests/tools/test_delegate_subagent_timeout_diagnostic.py \
  -q -o 'addopts='

Result:

8 passed, 1 warning

[alt-glitch]

Duplicate of #24888 — same fix: prefer TERMINAL_CWD over os.getcwd() in build_environment_hints() in prompt_builder.py. Multiple competing PRs for this fix: #24888, #24957, #24985, #27488, #29365.

[ArnBdev]

Closing at contributor request.