fix(env-client): reconnect when connect() is called from a different loop

[acharyaanusha]

Summary

EnvClient.connect() has a guard -- if self._ws is not None: return self -- that no-ops regardless of which event loop established that websocket. This breaks the officially documented pattern (docs/source/guides/async-sync.md):

client = await SomeClient.from_env(...)   # connects inside this loop
with client.sync() as sync_client:        # drives calls on a NEW, separate
    sync_client.reset()                   # background loop

from_env() ends with await client.connect(), binding _ws to whichever loop ran that await (e.g. an asyncio.run() call, which is closed by the time from_env() returns). .sync() then drives every later call through SyncEnvClient's own dedicated background-thread loop via run_coroutine_threadsafe. SyncEnvClient.connect() does call self._async.connect(), but the no-op guard returns immediately since _ws is already set -- so the websocket never gets rebound to the loop that's actually being used, and every reset()/step() call schedules work on a live loop while operating on a connection object tied to a dead one. The result is a hang or an asyncio "Future attached to a different loop" error.

Found this while building a training example (#853) that does exactly this combination. It's not specific to that example -- any from_env() + .sync() caller hits it, including the pattern in this repo's own async-sync guide.

Fix

• EnvClient now tracks which loop created _ws (self._ws_loop).
• connect() only treats an existing _ws as reusable if the current running loop matches _ws_loop; otherwise it drops the stale reference (unusable anyway, since its loop is typically already closed) and connects fresh on the current loop.
• disconnect() clears _ws_loop alongside _ws for consistency.

Test plan

• Added TestForeignLoopReconnect in tests/test_core/test_generic_client.py (3 cases): same-loop reconnect stays a no-op (no extra ws_connect call), a foreign-loop reconnect actually re-establishes the connection on the current loop, and disconnect() clears the loop-tracking state.
• pytest tests/test_core/ -q -- 190 passed, 11 pre-existing skips.
• ruff format --check / ruff check clean.

🤖 Generated with Claude Code