[Lane 3 · ios] Precision/Recall/F1 — iOS target parity check #1231

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

Lane: 3 · Platform verification · iOS
Skill needed: Kotlin/Native Apple (Xcode command-line tools, an iOS simulator runtime) 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. On a Mac with Xcode installed:
   ./gradlew :skainet-backends:skainet-backend-cpu:iosSimulatorArm64Test --tests "sk.ainet.exec.metrics.*"
2. If you have a device pipeline, iosArm64 is link-only in CI (no test runner); note
   that on the parent rather than trying to run it.

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

macosArm64Test is the closest sibling if the simulator runtime is missing; run it too
and say which you ran. See Contributing → Build from source for the toolchain setup.