chore(build): drop deprecated kotlin("stdlib-common") from KMP modules

Kotlin 2.x unified `kotlin-stdlib-common` into `kotlin-stdlib`, and the
kotlin-multiplatform plugin auto-adds the stdlib to commonMain. The
explicit `api(kotlin("stdlib-common"))` declarations are deprecated and
were the suspected (latent) cause of the metadata/JS classpath
regression tracked in #105. Removing them keeps build files current
with Kotlin 2.x and removes a footgun.

Verified across :llm-api, :llm-core, :llm-performance:
  compileCommonMainKotlinMetadata, compileKotlinJvm, compileKotlinJs
all build cleanly with --rerun-tasks --no-build-cache.

Refs #105.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: michalharakal

llm-api/build.gradle.kts

@@ -50,7 +50,6 @@ kotlin {
 
     sourceSets {
         commonMain.dependencies {
-            api(kotlin("stdlib-common"))
             api(libs.kotlinx.coroutines)
         }
 

llm-core/build.gradle.kts

@@ -43,7 +43,6 @@ kotlin {
 
     sourceSets {
         commonMain.dependencies {
-            api(kotlin("stdlib-common"))
             implementation(libs.skainet.lang.core)
             implementation(libs.skainet.compile.dag)
             implementation(libs.skainet.compile.opt)

llm-performance/build.gradle.kts

@@ -51,10 +51,6 @@ kotlin {
     }
 
     sourceSets {
-        commonMain.dependencies {
-            api(kotlin("stdlib-common"))
-        }
-
         commonTest.dependencies {
             implementation(libs.kotlin.test)
         }