DEV-203 Clear RFQ session cache on disconnect

[cesarenaldi]

Summary

• Clear the RFQ manager's cached session synchronously from the unexpected websocket close handler.
• Avoid returning a cached session once it is closing.
• Add integration coverage for reopening immediately from the failed quote wait after an unexpected disconnect.

Verification

• pnpm vitest --project client-integration packages/client/tests/integration/rfq.test.ts (completed; current test fixture skipped 24 tests)
• pnpm typecheck
• pnpm lint

Stacked on: #88
Linear: DEV-203

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Note

Medium Risk
Changes RFQ websocket session lifecycle and reconnect behavior in a trading path; scope is small and covered by a new integration test.

Overview
Fixes RFQ quoter reconnect after an unexpected websocket close by not reusing a dead cached session.

RfqQuoterWebSocketManager.connect() now drops the cached session when it is closing/closed and opens a new one instead of returning the stale handle. RfqWebSocketSession exposes a closed flag for that check. On socket close, #handleClose invokes the manager’s onClose callback before async shutdown so the cache is cleared synchronously when the connection drops.

Adds an integration test that quotes, forces the server to close mid-flight, then openRfqSession() again and expects a new session and a second connection.

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