Cover KMP source sets with a ktlint namespace-import rule

[StylianosGakis]

Stacked on #3110. Review that one first.

Why a second mechanism

The NamespaceImport Android Lint check from #3107 cannot reach KMP modules, so the 19 design system violations it just cleaned up are ones it could never have caught.

I tried to fix that properly before writing this:

Attempt	Result
Apply standalone com.android.lint alongside the KMP plugin	Works, catches commonMain. But every generateAndroidMainLintModel then depends on itself, and the build dies with a circular dependency as soon as two such modules depend on each other
checkDependencies = false	Same cycle
android.experimental.lint.analysisPerComponent=false	Same cycle
com.android.internal.lint	Runnable lint, but JVM components only. A full run with a planted violation still in commonMain came back green

The root cause is upstream. AGP's com.android.kotlin.multiplatform.library contributes a lint {} DSL but registers no task that runs it, and it sits outside com.android.base, so plugin logic keying off the Android plugins does nothing there. Google issue 246751841 has tracked this since 2022, AGP release notes through 9.3.2 never mention KMP lint, and the KMP plugin docs don't mention lint in either the supported or the unsupported section. The consistent community answer is to use ktlint or detekt for common code.

What this does

kotlinter already runs ktlint over every source set, so hedvig-ktlint implements the same rule as a RuleSetProviderV3 custom ruleset against ktlint 1.8.0, the version kotlinter 5.6.0 bundles. It is wired into every module through kotlinter's ktlint dependency configuration.

The tradeoff

ktlint has no type resolution, so unlike the Lint check it cannot ask whether an owner is a class or a package. CAPITALIZED_PACKAGES carries that cost: Kotlin/Native interop packages are named after the framework they bind, so platform.Foundation.systemLocale is shaped exactly like a member import and has to be excluded by prefix.

Both checks are kept deliberately. On Android modules Lint remains the better signal, since it resolves types and reports inline in the IDE as you type. A violation there is reported twice, which only happens when someone is already wrong.

Verification

• Fires on KMP commonMain: a planted import in Tooltip.kt reports [hedvig:namespace-import].
• Zero false positives. A full lintKotlin sweep across all 1,374 files and every source set returns no namespace-import hits.
• Edge cases pass: platform.Foundation.systemLocale in core-locale's nativeMain and every Duration.Companion.seconds import are clean.

Unrelated pre-existing failure worth knowing about

:feature-insurances and :feature-terminate-insurance currently fail lintKotlin on standard:indent, standard:wrapping and similar. I confirmed with a control run, changes stashed, that these are pre-existing and unrelated to this PR (38 identical errors). It does mean ktlintCheck is red on develop today.

[StylianosGakis]

Superseded, no content lost. See the reasoning in the comment on #3110.

The ktlint rule from this PR now leads the stack in #3122, since it is the mechanism with full coverage. The lint.xml change that was sitting in here unmentioned is extracted into #3121, together with a convention plugin fix so a new module no longer fails lint by existing.

• Fix two lint configuration traps #3121 (base develop) → Import the type, never the namespace #3122 (base Fix two lint configuration traps #3121) → Add a type-resolving NamespaceImport lint check #3123 (base Import the type, never the namespace #3122)

All three are drafts, rebased on current develop, and green.