Fold @param and @return KDoc tags into the description prose

[DmitryNekrasov]

The Kotlin coding convention recommends against @param/@return tags, preferring parameter and return descriptions inline in the prose with [name] links. This change applies that across the public KDoc in commonMain: each tag's content moves into the description, keeping all parameter constraints, defaults, and return behavior. @throws, @see, @sample, and @constructor are untouched, as are the already-compliant Long overloads of gcd/lcm and the count property.

Docs only, no API or behavior change. Dokka still generates cleanly, so every [name] link resolves (it runs with failOnWarning).