Periodic effects repeat ticks before their cadence at large clocks

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DISCLOSURE: LLM-GENERATED TEXT

Native Unity 6000.4.6f1 controls reproduced periodic effects executing 32 ticks per pass at an unchanged large clock, including before their initial delay. This can apply repeated damage or healing without elapsed time. This is a follow-up to #932's duration deadline sweep.

Source: Runtime/Tags/PeriodicEffectRuntimeState.cs initializes NextTickTime with float startTime + initialDelay and advances it with float += interval. At 2^24 or float.MaxValue, an interval of 1 can round back to the same timestamp.

Reproduction through EffectHandler's existing deterministic clock hooks, with an Infinite owner, interval 1, and unlimited ticks:

• Clock 100, delay 0: first pass 1 tick, repeated same-clock pass 0.
• Clock 100, delay 1: both passes 0.
• Clock 2^24 or float.MaxValue, delay 0 or 1: first pass 32, repeated same-clock pass 32. Delay 1 should produce zero before any elapsed time.

Fix the scheduler using elapsed time and a retained cadence offset, without relying on an absolute float deadline. Preserve inclusive due boundaries, minimum interval, bounded catch-up, maxTicks and per-handle ownership. Duration refresh/reapplication must retain the existing periodic phase; removing and applying a fresh handle must reset it. Keep public and serialized authoring fields unchanged.

Acceptance:

1. Add deterministic red-green runtime-state and actual-handler controls for ordinary and large clocks, backward clocks, exact boundaries, finite overflow, nonfinite values and repeated same-clock passes.
2. Preserve maxTicks, initial delay, interval clamp, catch-up cap, refresh/reapplication and reentrant removal behavior; sweep timing consumers.
3. Pass full native periodic/effect fixtures and default, SINGLE_THREADED, Odin and legacy typechecks; complete current-head CI on all supported versions/modes.
4. Update XML/feature docs and CHANGELOG. No timing or allocation claim without calibrated controls.

Provenance: session 348 PeriodicDeadlineProbe actual-handler native results, following commit 1bb4e4e in PR #933.

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DISCLOSURE: LLM-GENERATED TEXT

The deterministic tests now reproduce the defect before production changes. Native Unity 6000.4.6f1 ran 28 runtime-state cases: 21 passed and 7 failed. Six actual-handler cadence cases produced 2 passes and 4 failures; ordinary-clock controls passed, while unchanged large clocks repeated ticks or consumed them before the delay.

The sweep also found finite cancellation boundaries: a small start before a huge delay, and a small delay between opposing huge clocks. Independent review added elapsed subtraction and cadence product rounding controls, plus public tick-count rollover compatibility. These need retained arithmetic residuals and an independent scheduling count; merely widening an absolute deadline does not cover them.

Fix implementation and red-green acceptance are in progress in PR #933. Required full native fixtures, all compile branches, and final-head CI remain pending.

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DISCLOSURE: LLM-GENERATED TEXT

Fix and sweep: commit 37b2c09 in PR #933 preserves initial delay and periodic cadence using compensated finite timing and an independent scheduling count. It retains the public tick counter, live maxTicks, minimum interval, per-pass catch-up limit, refresh/reapplication phase, fresh-handle restart, and nonfinite comparison behavior.

Native Unity 6000.4.6f1 passed all 131 cases: scheduler 30, handler/reentrancy 96, behavior 3, and periodic authoring serialization 2. All host compilation variants, staged preflight, syntax reporting/equivalence controls, XML/member/comparison rules, documentation build, and spelling passed. Independent exact-rational diagnostics checked 56,188 finite cases with zero disagreements; a deliberately wrong scalar control failed 1,599. These diagnostics are not native or performance evidence.

XML, feature documentation and the short release note are updated. The batch is committed and pushed with a clean worktree. Required current-head CI is now running; the issue remains open until every supported version/mode and final feedback surface passes.