feat: Split summary counters and suppress individual events for override-affected evaluations

[kinyoklion]

Summary

This PR is stacked on #451 because it uses the override store and the marking that PR wires into the client.

This change carries the override-affected marking from evaluation into analytics events, as the OVERRIDE specification requires. Event handling keys on the marking scalar that the client hands to the event processor, not on the evaluation reason.

EvalEvent and record_eval_event gain an override_affected flag. The client sets it from the evaluation result for the evaluated flag, from each prerequisite record's own marking for prerequisite evaluations, and from the flag's own marker when an evaluation raises. An unknown flag is never marked.

The event dispatcher produces no individual feature event and no debug event for a marked evaluation, whatever the flag's configuration requests. Marked evaluations appear in summary events only. The summarizer keys counters by version, variation, and the marker, so override-affected and other evaluations of the same flag, variation, and version accumulate into separate counters. The summary event writes overrideAffected: true on the marked counters only, following the existing unknown marker. Event ingestion must accept that property on summary counters before release.

all_flags_state presents an override-affected flag with trackEvents false, trackReason false, and no debugEventsUntilDate, so a consumer bootstrapped from the state sends no individual events for it. The flag, its value, its version, and its reason stay in the state.

The specification vectors now also check the summary marker the client hands to the event processor for each evaluation.

Verification: processor specs (no feature event, no debug event, marked counter, counter split, unmarked counters unchanged, marked prerequisite record), summarizer spec (split by marker), client specs (record arguments for direct, segment, prerequisite, unknown, and error cases; all-flags tracking fields including experiment tracking and details-only-for-tracked), and end-to-end payload specs through the real event processor (index plus marked summary only for an overridden flag, individual events for an unaffected prerequisite inside a marked evaluation, ordinary events when nothing is overridden). Full suite and RuboCop are clean. Each new spec was checked against a deliberate defect in the code it covers.

The existing FDv1 and FDv2 file data sources keep their current behavior. This series does not change them; the override feature is additive.