fix(utils): advance the CPU tick baseline in systemInfoV2 getCurrentCpuTicks

[anxkhn]

What

getCurrentCpuTicks() in packages/utils/src/internals/systemInfoV2/cpu-info.ts
computes CPU load as the delta between the current os.cpus() tick counts and a
module-level previousTicks baseline, but it never wrote the new sample back to
previousTicks. The baseline therefore stayed at { idle: 0, total: 0 } for the
whole process, so every call returned the average CPU load since boot instead
of the load since the previous sample.

const previousTicks = { idle: 0, total: 0 };

export function getCurrentCpuTicks() {
    const cpusCores = os.cpus();
    const ticks = cpusCores.reduce(/* sum idle + total across cores */);
    const idleTicksDelta = ticks.idle - previousTicks.idle;
    const totalTicksDelta = ticks.total - previousTicks.total;
    // <- previousTicks was never updated here, so the delta is always measured from boot
    return totalTicksDelta ? 1 - idleTicksDelta / totalTicksDelta : 0;
}

Why it matters

systemInfoV2 is enabled by default, and getCurrentCpuTicks() is the CPU
fallback used in uncontainerized environments, cgroup-less containers and AWS
Lambda (the other branches use cgroup stats). Its result feeds
cpuCurrentUsage / isCpuOverloaded, which drive the AutoscaledPool. With a
frozen boot-average signal the CPU value barely moves for the rest of a run, so
CPU-based autoscaling never reacts to real load.

The intended contract is already established twice in the codebase:

• the V1 path LocalEventManager.createCpuInfo
  (packages/core/src/events/local_event_manager.ts) does the identical delta
  math and then Object.assign(this.previousTicks, ticks);
• the containerized branch in this same file advances its baseline with
  previousSample = sample.

getCurrentCpuTicks() was simply missing the equivalent write-back.

The fix

Write the sample back after computing the delta, mirroring both siblings:

const idleTicksDelta = ticks.idle - previousTicks.idle;
const totalTicksDelta = ticks.total - previousTicks.total;
Object.assign(previousTicks, ticks);
return totalTicksDelta ? 1 - idleTicksDelta / totalTicksDelta : 0;

The now-redundant non-null assertions (previousTicks!) on the non-null const are
dropped.

Test

Adds a regression test to test/utils/cpu-infoV2.test.ts that takes two samples
and asserts the second reflects the inter-sample delta (0.75) rather than the
cumulative-since-boot ratio (~0.583, which the buggy version returned). A
beforeEach resets the shared module baseline so the singleton state cannot leak
between tests.

Red -> green: against the unpatched source the new test fails
(expected 0.5833333333333333 to be close to 0.75); with the fix the file passes
18/18. test/core/autoscaling/ (snapshotter + system status + autoscaled pool)
also stays green at 39/39.