components: add OptionalFormSection (revealable form section)

The shared wrapper for optional edit-form fields behind a "More fields" toggle:
AnimatedVisibility with the family's expand+fade motion over a full-width Column.
Adds the first intra-kit dependency (components -> identity) for the shared
transitions.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

components/build.gradle.kts

@@ -33,6 +33,10 @@ kotlin {
 }
 
 dependencies {
+    // identity supplies the shared motion (expandEnter/collapseExit) that the
+    // revealable components animate with.
+    implementation(project(":identity"))
+
     implementation(platform(libs.androidx.compose.bom))
     implementation(libs.androidx.ui)
     implementation(libs.androidx.foundation)

components/src/main/kotlin/de/jeanlucmakiola/floret/components/FormSection.kt

@@ -0,0 +1,26 @@
+package de.jeanlucmakiola.floret.components
+
+import androidx.compose.animation.AnimatedVisibility
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.ColumnScope
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.Modifier
+import de.jeanlucmakiola.floret.identity.collapseExit
+import de.jeanlucmakiola.floret.identity.expandEnter
+
+/**
+ * A form section that reveals/hides with the family's expand+fade motion — the
+ * shared wrapper for the optional fields behind a "More fields" toggle in the
+ * edit forms. [content] is laid out in a full-width [Column].
+ */
+@Composable
+fun OptionalFormSection(visible: Boolean, content: @Composable ColumnScope.() -> Unit) {
+    AnimatedVisibility(
+        visible = visible,
+        enter = expandEnter(),
+        exit = collapseExit(),
+    ) {
+        Column(modifier = Modifier.fillMaxWidth(), content = content)
+    }
+}