feat: eignexCli version + generated BuildInfo source for --version

[rasros]

Closes #13.

What changed

• EignexCliExtension gains version, appName, appId, and buildInfoPackage properties.
• A new CC-safe generateCliBuildInfo task emits an internal object BuildInfo { NAME; ID; VERSION; versionLine() } into a generated commonMain source dir, wired via srcDir so it compiles across every KMP target (JVM + native) — mirroring the root build's generateKbuildVersion pattern.
• Defaults: version → project.version; appName → project name; appId → project group; buildInfoPackage → the package of mainClass (falling back to the group).

Why

--version is table stakes for a CLI, and the version should have one source of truth instead of a hand-maintained const val VERSION that drifts from the published/project version (and, for FlatZinc solvers, from the .msc). The awkward parts — a configuration-cache-safe codegen task, srcDir wiring across targets, and staying lint-clean — are exactly what the shared plugin should absorb.

Lint-clean

Generated under build/, so it's outside the detekt/checkKdoc src scan; and it's internal, so dokka (public API only) ignores it. The emitted KDoc has no [links]/angle-brackets, so even if scanned it's clean.

Scope

Kept in cli (not kmp/jvm): no library code hand-maintains a version today, cli doesn't apply kmp, and appName/appId/versionLine()/--version are CLI conventions. Base-layer exposure can be a future opt-in if a library ever needs a runtime version.

Testing

./gradlew compileKotlin passes. Functional generation is exercised by the klause-cli migration (drop the hand-maintained BuildInfo, set eignexCli { version/appName/appId }), to follow once this publishes.