test(core): RIP measured with Java FILIUS

RipRun runs rip-chain's three routers in Java FILIUS, each router's random
set by reflection to the core's ripSeed, and writes the frames, every
change of each RIP table and the calls. converge: the tables fill, a ping
at 45 s. expire: R3 falls silent at 10 s; R2 marks its network 16 hops only
at its own next beacon, R1 passes it on at once, the ping gets ICMP 3/0.
Both match: per sending card the same messages at the same times, every
table through the same states. The first 5 s are compared by the state the
tables reach, since Java's routers start one after the other.

Measured on the JDK: Java's pause divides nextFloat() by 3 in float; the
core does too now (a millisecond off in one draw of about 10,000 before).
Scenarios name their RIP routers in the new field rip.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

packages/core/src/runtime/random.ts

@@ -55,9 +55,13 @@ export class JavaCompatibleRandom {
     return (this.next(26) * 2 ** 27 + this.next(27)) / 2 ** 53;
   }
 
-  /** Java RIP: 30 s · (f/3 + 0.84), truncated — somewhere between 25.2 s and 35.2 s. */
+  /**
+   * Java RIP: 30 s · (f/3 + 0.84), truncated — somewhere between 25.2 s and
+   * 35.2 s. f/3 divides a float by an int, in float (JLS 5.6.2): one draw in
+   * about 10,000 comes out a millisecond apart from dividing in double
+   * (measured on OpenJDK 21).
+   */
   nextRipJitterMilliseconds(): number {
-    const javaFloat = this.nextFloat();
-    return Math.trunc(30_000.0 * (javaFloat / 3.0 + 0.84));
+    return Math.trunc(30_000 * (Math.fround(this.nextFloat() / 3) + 0.84));
   }
 }