test(tools): characterize tool-surface TERMINAL_CWD contract (#29265)

Port PR #29365's tool-surface contract test: terminal/file/execute_code
already honor TERMINAL_CWD (out of scope for the resolver cluster). Pinning
the behavior makes the supersession of #29365 airtight and guards against a
future refactor silently regressing the workspace contract.

tests/tools/test_gateway_cwd_contract.py

@@ -0,0 +1,69 @@
+"""Tool-surface cwd contract tests for gateway workspaces.
+
+These cover the platform-neutral part of #29265: once the gateway has resolved
+``TERMINAL_CWD``, the user-visible tool surfaces should agree on that workspace.
+
+Unlike the system-prompt readers fixed in the gateway-cwd-resolver cluster
+(agent/runtime_cwd.py), these tool sites already read ``TERMINAL_CWD``-first and
+were deliberately left out of scope. This file is a *characterization* guard: it
+pins the already-correct behavior so the supersession of PR #29365 is airtight
+and a future refactor of these sites can't silently regress the contract.
+"""
+
+from __future__ import annotations
+
+from pathlib import Path
+
+from tools import code_execution_tool, file_tools, terminal_tool
+
+
+def test_terminal_env_config_uses_terminal_cwd(monkeypatch, tmp_path):
+    """The terminal tool's default cwd should come from TERMINAL_CWD."""
+    workspace = tmp_path / "workspace"
+    workspace.mkdir()
+
+    monkeypatch.setenv("TERMINAL_ENV", "local")
+    monkeypatch.setenv("TERMINAL_CWD", str(workspace))
+
+    config = terminal_tool._get_env_config()
+
+    assert config["cwd"] == str(workspace)
+
+
+def test_file_tool_relative_paths_use_terminal_cwd(monkeypatch, tmp_path):
+    """Relative file/search/patch paths resolve under TERMINAL_CWD."""
+    workspace = tmp_path / "workspace"
+    workspace.mkdir()
+
+    monkeypatch.setenv("TERMINAL_CWD", str(workspace))
+
+    resolved = file_tools._resolve_path_for_task("notes/today.md", task_id="cwd-contract")
+
+    assert resolved == (workspace / "notes" / "today.md").resolve()
+
+
+def test_execute_code_project_mode_uses_terminal_cwd(monkeypatch, tmp_path):
+    """Project-mode execute_code should run scripts from TERMINAL_CWD."""
+    workspace = tmp_path / "workspace"
+    staging = tmp_path / "staging"
+    workspace.mkdir()
+    staging.mkdir()
+
+    monkeypatch.setenv("TERMINAL_CWD", str(workspace))
+
+    resolved = code_execution_tool._resolve_child_cwd("project", str(staging))
+
+    assert Path(resolved) == workspace
+
+
+def test_execute_code_project_mode_falls_back_when_terminal_cwd_missing(monkeypatch, tmp_path):
+    """Invalid TERMINAL_CWD should not break execute_code project mode startup."""
+    staging = tmp_path / "staging"
+    staging.mkdir()
+
+    monkeypatch.setenv("TERMINAL_CWD", str(tmp_path / "missing"))
+
+    resolved = code_execution_tool._resolve_child_cwd("project", str(staging))
+
+    assert Path(resolved).is_dir()
+    assert Path(resolved) != tmp_path / "missing"