fix(cli): accept Kotlin source directory in cap doctor

[fabiomartino]

Description

cap doctor reports a false positive for Android projects that use Kotlin as their only source language. The main activity check in @capacitor/cli probes only app/src/main/java for the MainActivity, so projects that place their source in app/src/main/kotlin (the documented plugin authoring language) fail with:

java directory is missing in android/app/src/main/java

even though the app is perfectly valid.

This PR makes the check accept either source directory: it probes both java and kotlin under src/main, fails only when neither exists, and scans whichever are present (the file filter already accepted .kt files).

Change Type

• Fix
• Feature
• Refactor
• Breaking Change
• Documentation
• Other (CI, chores, etc.)

Rationale / Problems Fixed

Kotlin-only Capacitor apps trigger a misleading doctor error that makes a healthy project look broken. The fix removes the false positive without weakening the check for genuinely missing source layouts.

Tests or Reproductions

• npx jest -i test/doctor.android.spec.ts — new suite with 5 cases: Kotlin-only passes, Java-only passes (no regression), both directories pass, neither directory rejects with the updated message, Kotlin without a MainActivity still rejects with Main activity file (...) is missing.
• npx jest -i — 57 tests pass across 9 suites. The 4 failing suites (migrate-uiscene-*, xcode.spec.ts) are pre-existing environment failures unrelated to this change (missing @types/xcode in the dev node_modules).
• npx tsc --noEmit — no new errors.

Screenshots / Media

N/A

Platforms Affected

• Android
• iOS
• Web

Notes / Comments

The error message changes from java directory is missing in ... to java or kotlin directory is missing in ... so it stays accurate for both layouts.