fix(cli): guard gateway abort during turn cancellation

[lihongguang0014]

Fixes #1505

Problem

Pressing Ctrl+C to interrupt an in-flight gateway turn while the connection is already lost let the ConnectionError raised by abort_session escape the KeyboardInterrupt/CancelledError handler and crash the turn instead of returning TurnResult(cancelled=True), so the REPL could not re-prompt.

Root cause

src/opensquilla/cli/chat/turn_stream.py awaits client.abort_session(session_key) inside the except (KeyboardInterrupt, asyncio.CancelledError) block. GatewayClient._call() raises ConnectionError when the connection is gone (src/opensquilla/cli/gateway_client.py). An exception raised inside an except block escapes it, so the turn never reaches the graceful cancel path — and connection loss is exactly when users press Ctrl+C.

Fix

Wrap the abort call in try/except Exception (minimal change, 7 lines). The turn is already cancelled locally; the abort RPC is best-effort.

Test

Adds regression test test_gateway_stream_interrupt_tolerates_abort_failure in tests/test_cli/test_chat_cmd.py: send_message raises KeyboardInterrupt and abort_session raises ConnectionError; asserts TurnResult.cancelled is True. Verified the test fails on unfixed code and passes with the fix; all 63 tests in the file pass.