test(issue31): keep every claude tmp root candidate inside the test

The adapter's fixed /tmp fallback is now a module constant. The new tests
point it, TMPDIR, TMP and TEMP at the test's own dirs, in the test process
and (through a sitecustomize on PYTHONPATH) in every python a test starts,
so no test lists the real /tmp/claude-<uid> any more (Mac review, PR #59).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.agents/skills/lib_py/agents/adapters/claude.py

@@ -22,6 +22,10 @@ def _projects_dirs(ctx: DiscoveryContext) -> list:
     return dirs
 
 
+# Node's os.tmpdir() when no TMPDIR/TMP/TEMP is set; tests point it elsewhere.
+_SYSTEM_TMP = "/tmp"
+
+
 def _tmp_roots() -> list:
     """The per-uid temp roots claude may have used: ${CLAUDE_CODE_TMPDIR:-
     os.tmpdir()}/claude-<uid>. A sandboxed tool shell sets CLAUDE_CODE_TMPDIR
@@ -36,9 +40,9 @@ def _tmp_roots() -> list:
             cands.append(override)
     # Node's os.tmpdir() on POSIX, not tempfile.gettempdir() (which probes
     # writability and falls back to the cwd).
-    tmp = os.environ.get("TMPDIR") or os.environ.get("TMP") or os.environ.get("TEMP") or "/tmp"
+    tmp = os.environ.get("TMPDIR") or os.environ.get("TMP") or os.environ.get("TEMP") or _SYSTEM_TMP
     cands.append(os.path.join(tmp.rstrip("/") or "/", name))
-    cands.append(os.path.join("/tmp", name))
+    cands.append(os.path.join(_SYSTEM_TMP, name))
     roots, seen = [], set()
     for c in cands:
         real = os.path.realpath(c)