fix: emit close after normal WebSocket shutdown

[harley-poly]

Changes

Emit close when a remote WebSocket shuts down normally. Previously, close codes 1000 and 1001 ended the receive loop without notifying subscribers.

Add real connection regressions for both markets and private streams, including abnormal closes, local close, cancellation and listener errors. Bump the package version to 1.0.2 for the existing publishing workflow.

Testing

• 162 tests pass on Python 3.10–3.13 with current compatible dependencies, and on Python 3.10 with websockets==13.0.
• The four normal-close regression cases fail against the original implementation.
• Ruff lint/format, mypy, and wheel/sdist build pass.

Checklist

• Tests pass (pytest)
• Linting passes (ruff check .)
• Types check (mypy polymarket_us)

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Note

Low Risk
Small, targeted change to event emission on disconnect plus regression tests; no auth or API contract changes.

Overview
Fixes WebSocket lifecycle signaling so subscribers get a close event when the server ends the stream without raising ConnectionClosed (e.g. normal close codes 1000/1001). BaseWebSocket._message_loop now emits close in the try/except else branch after the receive loop exits cleanly, while existing behavior for ConnectionClosed, listener failures (error), and client-initiated shutdown (cancelled task, no extra close) stays the same.

Adds TestWebSocketLifecycle integration tests for markets and private streams (remote close codes, local close, task cancellation, heartbeat listener errors). Package version is bumped to 1.0.2.

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