refactor: real-home and terminal temp-dir fallbacks stop naming /tmp

get_real_home() fell back to a literal /tmp when no OS home could be found, and
LocalEnvironment.get_temp_dir() probed /tmp by hand before consulting
tempfile.gettempdir(), whose own candidate walk already covers the system temp
dir (and honours the scratch TMPDIR Hermes now exports). Both defer to
tempfile.gettempdir(); a relative gettempdir() result is made absolute instead of
being swapped for /tmp.

hermes_constants.py

@@ -921,7 +921,8 @@ def get_real_home(env: dict[str, str] | None = None) -> str:
         seen.add(key)
         if not _is_profile_home(candidate, profile_home):
             return candidate
-    return "/tmp"
+    import tempfile
+    return tempfile.gettempdir()
 
 
 _HOME_MODE_ALIASES = {"isolated": "profile", "profile_home": "profile", "profile-home": "profile",

tools/environments/local.py

@@ -826,8 +826,8 @@ class LocalEnvironment(BaseEnvironment):
 
     def get_temp_dir(self) -> str:
         """Shell-safe writable temp dir. Precedence: ``TERMINAL_TEMP_DIR``, TMPDIR/TMP/TEMP
-        (Termux has no /tmp), ``HERMES_HOME/cache/terminal`` (real storage: tmpfs /tmp
-        fills under Hermes load; pruned by ``cleanup_terminal_temp_cache``), /tmp,
+        (Termux has no system temp dir), ``HERMES_HOME/cache/terminal`` (real storage: a
+        tmpfs system temp dir fills under Hermes load; pruned by ``cleanup_terminal_temp_cache``),
         ``tempfile.gettempdir()``; backend env before process env so terminal.env
         overrides work. Windows: ``%TEMP%`` often has spaces that break unquoted bash,
         so always the HERMES_HOME cache dir with forward slashes (bash- and Python-valid)."""
@@ -853,10 +853,9 @@ class LocalEnvironment(BaseEnvironment):
                 return _posix(resolved)
         except Exception:
             pass
-        if os.path.isdir("/tmp") and os.access("/tmp", os.W_OK | os.X_OK):
-            return "/tmp"
+        # tempfile's own candidate walk already covers the system temp dir.
         fallback = tempfile.gettempdir()
-        return _posix(fallback) if fallback.startswith("/") else "/tmp"
+        return _posix(fallback if fallback.startswith("/") else os.path.abspath(fallback))
 
     @staticmethod
     def _quote_cwd_for_cd(cwd: str) -> str: