[Lane 3 · native] Precision/Recall/F1 — Kotlin/Native (macOS/Linux) target parity check #1233

Sub-issue of #1222 (Precision, Recall and F1Score metrics).

Lane: 3 · Platform verification · Kotlin/Native (macOS / Linux)
Skill needed: Kotlin/Native desktop targets build tooling — running a Kotlin Multiplatform module's tests on this target. No tensor-internals or metrics knowledge required. The code under test is pure commonMain Kotlin over Double counters; this is a smoke check, not new implementation.
Size: xs (~30–60 min)
Blocked by: #1229 (F1Score merged to develop), or check out its branch early.

What to do

1. macOS Apple Silicon: ./gradlew :skainet-backends:skainet-backend-cpu:macosArm64Test --tests "sk.ainet.exec.metrics.*"
2. Linux x86-64: ./gradlew :skainet-backends:skainet-backend-cpu:linuxX64Test --tests "sk.ainet.exec.metrics.*"
   (linuxArm64 is link-only — note it rather than run it).
3. Run at least one of the two; say which.

Then, in every case:

• Confirm the metric tests (sk.ainet.exec.metrics.*) pass and the values match the JVM run
  bit-for-bit — pure Long counting and Double division, so any drift is itself a finding.
• Report on [Feature]: Precision, Recall and F1Score metrics #1222: target, toolchain versions, pass/fail, wall-clock, anything
  target-specific you hit (an expect/actual gap, a disabled test source set, a task
  that doesn't exist).

Acceptance

• Result posted on [Feature]: Precision, Recall and F1Score metrics #1222 with the exact Gradle task(s) run
• If something is wrong, a separate bug issue opened and linked — don't block the
  parent on investigating it here

Notes

The CI matrix in .github/workflows/native-cpu-multiarch.yml shows which native targets
CI already exercises — if the metric tests are picked up there automatically after
#1229 merges, a link to the green run is an acceptable report.