Implemented the next missing parity slice around session-scoped environment variables.

src/session_env_vars.py

@@ -0,0 +1,46 @@
+"""Session-scoped environment variables — Python port of
+``utils/sessionEnvVars.ts``.
+
+These are env vars set during a session (via the upstream ``/env`` slash
+command in npm) and applied only to spawned child processes — not to the
+host Python REPL/agent process itself. Bash and similar tool providers
+read this map to merge into ``subprocess`` environments.
+
+Mirrors the upstream module-level singleton: callers import the helpers
+directly rather than passing a registry around.
+"""
+
+from __future__ import annotations
+
+from collections.abc import Mapping
+from types import MappingProxyType
+
+_session_env_vars: dict[str, str] = {}
+
+
+def get_session_env_vars() -> Mapping[str, str]:
+    """Return a read-only view of the current session env vars."""
+    return MappingProxyType(_session_env_vars)
+
+
+def set_session_env_var(name: str, value: str) -> None:
+    """Set ``name=value`` for the rest of this session's child processes."""
+    _session_env_vars[name] = value
+
+
+def delete_session_env_var(name: str) -> None:
+    """Remove ``name`` from the session env (no-op if absent)."""
+    _session_env_vars.pop(name, None)
+
+
+def clear_session_env_vars() -> None:
+    """Drop every session-scoped env var."""
+    _session_env_vars.clear()
+
+
+__all__ = [
+    'get_session_env_vars',
+    'set_session_env_var',
+    'delete_session_env_var',
+    'clear_session_env_vars',
+]