[beekld]

Summary

The FDv2 synchronizer loop measured its deadlines against the wall clock. When the system clock stepped backwards, every pending deadline was delayed by the size of the step. If every synchronizer was parked for 5 minutes and the clock stepped back an hour, no synchronizer ran for 65 minutes.

These deadlines now use MonotonicTime, a small value class over System.nanoTime(), so changes to the system clock don't move them.

Stacked on #252.

---

Note

Overview
Fixes FDv2 synchronizer orchestration so recovery, fallback, park/unpark, and FDv1 fallback TTL deadlines no longer use the wall clock (Instant). A backward system clock step could stretch those waits far beyond the configured delays (e.g. a 5-minute park becoming 65 minutes after a 1-hour step back).

Adds MonotonicTime, a small wrapper around System.nanoTime() with plus, isBefore, and until, and wires it through FDv2DataSource, SourceManager, and SynchronizerFactoryWithState for deadline scheduling and awaitUntil timeouts. MonotonicTimeTest covers comparison and duration math when the nano counter overflows.

^{Reviewed by Cursor Bugbot for commit 7a1fa34. Bugbot is set up for automated code reviews on this repo. Configure here.}