fix(socket.io): Deduplicate disconnect listener in bindMessageHandlers

[fru1tworld]

Summary

Cache the disconnect$ observable per socket using a WeakMap so that multiple gateways sharing the same Socket.IO server register only one disconnect listener per client socket instead of one per gateway.

Changes

• Added a WeakMap<Socket, Observable> to IoAdapter to cache disconnect$ per socket.
• bindMessageHandlers now reuses the cached observable on subsequent calls for the same socket.
• Added unit test verifying a single disconnect listener is registered regardless of call count.

Manual test / verification

• npm run test — all 2003 unit tests passing.
• npx prettier --check — formatting OK.
• npm run lint:packages — no errors.

Fixes #7249

[coveralls]

Coverage Report for CI Build 26

Coverage remained the same at 89.907%

Details

• Coverage remained the same as the base build.
• Patch coverage: No coverable lines changed in this PR.
• No coverage regressions found.

Uncovered Changes

No uncovered changes found.

Coverage Regressions

No coverage regressions found.

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Coverage Stats

Relevant Lines:	8461
Covered Lines:	7607
Line Coverage:	89.91%
Relevant Branches:	2859
Covered Branches:	2316
Branch Coverage:	81.01%
Branches in Coverage %:	No
Coverage Strength:	21.18 hits per line

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💛 - Coveralls