identity: draw the M3 Expressive theme factory + nav slide from floret-kit

Phase 3 (identity layer). AgendulaTheme is now a thin wrapper over the kit's
FloretExpressiveTheme(lightScheme, darkScheme, …): the shared mechanics
(dynamic colour, light/dark, standard motion scheme) live in floret-kit, while
Agendula keeps its own identity — the seed-derived AgendulaLight/DarkFallback
schemes and AgendulaTypography (unchanged in Color.kt/Type.kt). rememberNavSlideSpec
now comes from the kit; the app's AgendulaTransitions.kt is removed and the
NavHost import repointed. Submodule re-pinned to the identity kit commit.

Clean composite build + tests + lintDebug + debug assemble green; substitution
confirmed (de.jeanlucmakiola.floret:identity -> project :floret-kit:identity).

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

app/build.gradle.kts

@@ -122,6 +122,7 @@ dependencies {
     implementation(libs.kotlinx.coroutines.core)
     implementation("de.jeanlucmakiola.floret:core-time")
     implementation("de.jeanlucmakiola.floret:core-crash")
+    implementation("de.jeanlucmakiola.floret:identity")
 
     debugImplementation(libs.androidx.ui.tooling)
     debugImplementation(libs.androidx.ui.test.manifest)