v2: make the pure modules Kotlin Multiplatform (iOS port, phase 0)

[jaydeetay]

Description

Phase 0 of the iOS port: the pure modules become Kotlin Multiplatform, so an iOS app can share
the math, astronomy, catalog, events and renderer-contract code instead of reimplementing it.
Android is unchanged. The Android modules and :data:generator consume each module's jvm
target exactly as they consumed the old kotlin("jvm") jar, and the generated skymap.db is
byte-identical.

Stacked on #1058. The eventual Metal backend follows the GLES3 backend; GLES1 is not ported.

Build

• New skymap.pure-kmp convention: jvm + iosArm64 + iosSimulatorArm64 + iosX64 (the
  last one for simulators on Intel Macs). :core:math, :core:astronomy, :core:catalog,
  :core:events and :render:api use it. :data:generator and :konsist stay on
  skymap.pure-kotlin as JVM tools.
• Sources moved to src/commonMain with git mv, so history is kept.
• One expect/actual: NameNormalizer's NFD step (java.text.Normalizer on the JVM,
  Foundation on Apple). Plus two imports (kotlin.concurrent.Volatile, kotlin.jvm.JvmInline).

Tests run on every target

• All suites moved to commonTest. Truth is JVM-only, so the new :core:testing provides
  Truth's names and semantics for exactly the subset in use. Each suite changed only its
  imports, plus assertThrows → assertFailsWith and a few JDK calls. The shim's own tests pin
  that every assertion can fail.
• Kotlin/Native rejects commas in backtick test names, so ten names swap , for -.
• The first iOS run found a real bug: Kotlin/Native's regex engine rejects \p{N}, so
  NameNormalizer could not even initialise on iOS. It now spells N out as
  \p{Nd}\p{Nl}\p{No}, which is the same set, and a new test covers Nl/No.
• Search agrees across platforms. The catalog DB is normalized on the JVM, but each
  platform normalizes search queries itself. NameNormalizerCorpusTest re-normalizes all
  12,516 catalog names (exported by the new :data:generator:exportNameCorpus) on every target
  and requires the JVM's result. All agree on the iOS simulator. With the Apple NFD step
  disabled, it reports 2,109 mismatches, so the check isn't vacuous.
• On a Mac with only the Command Line Tools, check skips the iOS link/test tasks with a
  warning instead of failing, so Android-only setups keep working.

Konsist: closes the :core:events gap, admits :core:testing, and bans java.*/javax.*
in the shared modules' non-jvm source sets. (Checked with probe files: the import fails the
gate in commonMain and passes in jvmMain.)

CI: a new macos-15 job runs iosSimulatorArm64Test.

Type of Change

• Bug fix
• New feature (Sky Map team only)
• Translation (new or updated)
• Documentation
• Refactoring / code cleanup
• Dependency upgrade
• Other

Checklist

• I've read the contributing guidelines
• For major changes, I've emailed skymapdevs@gmail.com first
• I've run the unit tests (./gradlew check from stardroid-v2/, or ./gradlew :app:test
  from stardroid-v1/, matching whichever module this PR touches)
• I've tested on a device/emulator if applicable
• If I have multiple commits, I've squashed them into one

No need to update CHANGELOG.md - we'll get Claude to do that when we cut a release.

Notes for Reviewers

• Verified locally (Intel Mac, Xcode 26.6, iOS 26.5 simulator): ./gradlew check is green,
  and all 340 tests pass on both the JVM and the iOS simulator (iosX64Test). Per-module JVM
  counts match the pre-conversion suites, plus the shim's 12 tests, the new NameNormalizer
  case and the corpus test.
• Not yet verified: the new macOS CI job. The workflow only triggers on PRs to master, so
  it won't run on this stacked PR until it is retargeted after v2: a selectable GL ES 3.0 renderer backend beside GLES1 #1058 merges (or is dispatched by
  hand on this branch).
• Review mostly as renames. git diff -M shows almost every file as R09x with import-only
  changes. The substance is in build-logic/.../skymap.pure-kmp.gradle.kts, core/testing/,
  NameNormalizer*.kt, RecordingSkyRenderer.kt (ConcurrentHashMap → a common atomic
  reference) and ArchitectureTest.kt.
• Docs: build-and-tooling.md has a new Kotlin Multiplatform section; code-overview.md,
  high-level-architecture.md and AGENTS.md are updated for the layout.

🤖 Generated with Claude Code

[github-actions]

PR Code Suggestions ✨

Explore these optional code suggestions:

Category	Suggestion	Impact
Possible issue	Avoid failing if allTests task absent Registering a configuration hook on tasks.named("allTests") causes Gradle configuration failure whenever allTests is not created by the KMP plugin (for example, when running tasks on Linux/Windows where Apple targets are automatically omitted, or when targets are disabled). Avoid tasks.named("allTests") and instead use tasks.matching { it.name == "allTests" }.configureEach { ... } or conditionally locate it with tasks.findByName to prevent UnknownTaskException. stardroid-v2/build-logic/src/main/kotlin/skymap.pure-kmp.gradle.kts [57-79] if (System.getProperty("os.name").startsWith("Mac")) { val xcodeInstalled = providers .exec { commandLine("xcrun", "xcodebuild", "-version") isIgnoreExitValue = true }.result .map { it.exitValue == 0 } tasks.withType<KotlinNativeLink>().configureEach { onlyIf("Xcode is installed") { xcodeInstalled.get() } } tasks.withType<KotlinNativeTest>().configureEach { onlyIf("Xcode is installed") { xcodeInstalled.get() } } - tasks.named("allTests") { + tasks.matching { it.name == "allTests" }.configureEach { val modulePath = path doFirst { if (!xcodeInstalled.get()) { logger.warn("$modulePath: iOS tests SKIPPED — Xcode is not installed.") } } } } Suggestion importance[1-10]: 8 __ Why: On macOS without Apple targets active or depending on Kotlin Multiplatform lifecycle task registration timing, tasks.named("allTests") will throw UnknownTaskException during configuration if allTests does not exist. Using tasks.matching { it.name == "allTests" }.configureEach prevents Gradle configuration from breaking unexpectedly.	Medium