fix(runtime): update shell session wire protocol

[priyasingh2111]

Description

Simplify shell session connection and lifecycle to improve performance and align with updated server behavior.

Changes:

• Faster connection — shell is ready immediately after WebSocket opens. Removed unnecessary handshake wait that added up to 10s latency.
• close() now detaches instead of terminating — closing the session disconnects the WebSocket but leaves the shell alive on the server, enabling reconnection within the reconnect window.
• Removed shell.reconnected and shell.bytesDropped properties — these are no longer available. TypeScript will report a compile error if accessed.
• Updated onReconnect callback signature — now () => void | Promise<void> (no arguments).

Exit codes, auto-reconnect, and all other shell functionality continue to work as before.

Related Issues

Documentation PR

Type of Change

Breaking change

Breaking Changes

• shell.reconnected — removed (was boolean)
• shell.bytesDropped — removed (was number)
• onReconnect callback signature: (reconnected: boolean) => void → () => void | Promise<void>
• close() no longer terminates the shell — it detaches, allowing reconnection

Testing

• I ran npm run check
• npm test — 616 tests pass (24 files), 1.13s
• npm run lint — clean
• npm run format:check — clean
• npm run type-check — clean
• Integration tested against live runtime (8/8 scenarios pass)

Checklist

• I have read the CONTRIBUTING document
• I have added any necessary tests that prove my fix is effective or my feature works
• I have updated the documentation accordingly
• I have added an appropriate example to the documentation to outline the feature, or no new docs are needed
• My changes generate no new warnings
• Any dependent changes have been merged and published

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