fix: preserve client modifiers when emit aborts

[electrohyun]

Summary

Keeps client Socket modifiers until an emit is dropped as volatile, buffered, or successfully encoded and scheduled. Outgoing observer and payload-encoding failures therefore preserve the pending modifier for the next completed emit, matching Socket.IO.

Shared real/mock cases cover both failure modes, one-shot consumption, reserved-event retention, and the unchanged Server Socket control. ADR 0026 and the generated conformance report record the consumption boundary.

Related issue

Closes #361

Checklist

• Tests added or updated
• Behavior verified against real socket.io

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Run ID: 6411c422-13de-4f23-9a66-ae89940b7fac

📥 Commits

Reviewing files that changed from the base of the PR and between 59690e6 and 6d7e904.

📒 Files selected for processing (6)

• docs/conformance.md
• docs/decisions/0026-payloads-cross-a-json-snapshot-boundary.md
• src/on-any-outgoing.test.ts
• src/payload-serialization.test.ts
• src/reserved-events.test.ts
• src/runtime/sockets.ts

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📝 Walkthrough

Walkthrough

The client now consumes modifiers after outgoing observation and packet encoding. Regression tests cover listener exceptions, encoding failures, and reserved-event rejection. Conformance documentation and the payload decision record describe the updated behavior.

Changes

Client modifier retention

Layer / File(s)	Summary
Modifier consumption boundary src/runtime/sockets.ts, docs/decisions/0026-payloads-cross-a-json-snapshot-boundary.md	ClientSocket.sendEvent retains active flags through outgoing observation and packet creation, then consumes them on each exit path.
Regression coverage src/on-any-outgoing.test.ts, src/payload-serialization.test.ts, src/reserved-events.test.ts	Tests verify timeout retention after outgoing listener errors, payload encoding failures, and rejected reserved events.
Conformance updates docs/conformance.md	Conformance entries and source links cover the new timeout-retention cases.

Estimated code review effort: 2 (Simple) | ~10 minutes

Merge Risk: ⚪ Minimal · up to 6d7e9

The PR preserves client modifiers when an emit aborts and adds coverage for the affected cases. No actionable merge-blocking risk remains after normal validation and review.

Possibly related PRs

• electrohyun/smocket#134: Related outgoing catch-all behavior and timeout handling.
• electrohyun/smocket#258: Related payload snapshot and encoding behavior.
• electrohyun/smocket#271: Related modifier-flag consumption in ClientSocket.sendEvent.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly identifies preserving client modifiers when an emit aborts, which is the primary change.
Description check	✅ Passed	The description explains the client modifier behavior, implementation boundary, tests, documentation, and linked issue.
Linked Issues check	✅ Passed	The changes address issue #361 by preserving client modifiers after observation or encoding failures and retaining existing reserved-event and server behavior.
Out of Scope Changes check	✅ Passed	The runtime change, regression tests, ADR, and conformance documentation all support the linked issue objectives.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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