feat: Mark override-affected evaluations in analytics events

[kinyoklion]

Summary

This is the fourth step of the flag overrides port described by the OVERRIDE specification. It is based on the override store branch because the phases are stacked; retarget to feat/overrides once that branch merges.

EventInputEvaluation gains override_affected, set by the client for the top-level evaluation and by the evaluator for each prerequisite record from that record's own marking. The event processor keys on this scalar alone and never reads the evaluation reason: an override-affected evaluation produces no individual feature event and no debug event, even when the flag requests them, while its index event and its summary counting are unchanged. An unaffected prerequisite record inside a marked evaluation is still recorded as usual.

The summary counter key becomes (variation, version, override_affected), so override-affected and ordinary evaluations of the same flag, variation, and version accumulate into separate counters instead of collapsing together. A counter that aggregates marked evaluations carries overrideAffected: true in the summary event; the property is present only when true, like the unknown marker. Both the sync and async event processors share this dispatch and output code.

In the all-flags state, an override-affected flag keeps its value, version, and marked reason but is presented with trackEvents and trackReason off and no debugEventsUntilDate, so a consumer bootstrapped from the state sends no individual events for it. When a migration evaluation of an overridden flag replaces the reason with a wrong-type error, the new reason keeps the marking. The async client mirrors these changes.

The OVERRIDE specification vector runner now also asserts the summaryOverrideAffected field of each vector against the marking the client hands to the event processor.

Tests cover the summarizer key split, the marker in the summary output, suppression of feature and debug events through both real event processors (including a marked prerequisite record and a mixed set of evaluations of one flag), the client-side marking of top-level and prerequisite records through a prerequisite tree, the all-flags tracking fields, the wrong-type reason, and an end-to-end payload check that an override-affected flag appears only in the summary.

SDK-3250

An evaluation that fails with an unexpected exception keeps the marking when the flag came from the override layer, so it produces no individual event and the all-flags state presents it with tracking off.

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Note

Overview
Adds override_affected on evaluation analytics records so flag-override evaluations are handled differently from normal traffic in sync and async clients.

Event pipeline: Override-affected evaluations still update summary counters and index events, but no individual feature or debug events—even when the flag has tracking or debug enabled. Summary counters are keyed by (variation, version, override_affected) so marked and unmarked evaluations do not merge; marked counters emit overrideAffected: true in the summary payload.

Client wiring: Top-level eval events pass result.override_affected from the evaluator; prerequisite eval events pass each prereq’s own marking. WRONG_TYPE (migration) and EXCEPTION paths preserve overrideAffected on the reason and set the event flag when the definition came from the override layer. all_flags_state clears trackEvents, trackReason, and debugEventsUntilDate for override-affected flags so bootstrapped consumers do not emit per-flag events.

Async FDv2: Flag-change notifications after client close no longer raise when the event loop is closed (notification is dropped with a debug log).

Tests: New coverage for summarizer/processor behavior, OVERRIDE spec vectors (summaryOverrideAffected), and client scenarios (prereq trees, failures, end-to-end HTTP payloads).

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[kinyoklion]

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