Add Android build target and responsive/drawer UI for phones and tablets

Restructure src-tauri into lib+bin (Tauri 2's mobile requirement — Android
embeds the app as a JNI cdylib, which needs a [lib] target with
tauri::mobile_entry_point) and scaffold gen/android/ via `cargo tauri
android init`. Builds and packages cleanly to a debug APK/AAB.

pcd_viewer.html: the 284px docked sidebar becomes a slide-in drawer under
768px viewport width (toggled from the rail, closes on backdrop tap), the
rail sheds its subtitle and secondary telemetry chips under 480px, and the
camera panel caps its width to the viewport. Also disables native pinch-zoom
(the canvas has its own via OrbitControls) and sets overscroll-behavior:none
for a full-bleed touch surface.

src-tauri/gen/android/buildSrc/build.gradle.kts

@@ -0,0 +1,23 @@
+plugins {
+    `kotlin-dsl`
+}
+
+gradlePlugin {
+    plugins {
+        create("pluginsForCoolKids") {
+            id = "rust"
+            implementationClass = "RustPlugin"
+        }
+    }
+}
+
+repositories {
+    google()
+    mavenCentral()
+}
+
+dependencies {
+    compileOnly(gradleApi())
+    implementation("com.android.tools.build:gradle:8.11.0")
+}
+

src-tauri/gen/android/buildSrc/src/main/java/com/khj/pcdviewer/kotlin/BuildTask.kt

@@ -0,0 +1,68 @@
+import java.io.File
+import org.apache.tools.ant.taskdefs.condition.Os
+import org.gradle.api.DefaultTask
+import org.gradle.api.GradleException
+import org.gradle.api.logging.LogLevel
+import org.gradle.api.tasks.Input
+import org.gradle.api.tasks.TaskAction
+
+open class BuildTask : DefaultTask() {
+    @Input
+    var rootDirRel: String? = null
+    @Input
+    var target: String? = null
+    @Input
+    var release: Boolean? = null
+
+    @TaskAction
+    fun assemble() {
+        val executable = """cargo""";
+        try {
+            runTauriCli(executable)
+        } catch (e: Exception) {
+            if (Os.isFamily(Os.FAMILY_WINDOWS)) {
+                // Try different Windows-specific extensions
+                val fallbacks = listOf(
+                    "$executable.exe",
+                    "$executable.cmd",
+                    "$executable.bat",
+                )
+                
+                var lastException: Exception = e
+                for (fallback in fallbacks) {
+                    try {
+                        runTauriCli(fallback)
+                        return
+                    } catch (fallbackException: Exception) {
+                        lastException = fallbackException
+                    }
+                }
+                throw lastException
+            } else {
+                throw e;
+            }
+        }
+    }
+
+    fun runTauriCli(executable: String) {
+        val rootDirRel = rootDirRel ?: throw GradleException("rootDirRel cannot be null")
+        val target = target ?: throw GradleException("target cannot be null")
+        val release = release ?: throw GradleException("release cannot be null")
+        val args = listOf("tauri", "android", "android-studio-script");
+
+        project.exec {
+            workingDir(File(project.projectDir, rootDirRel))
+            executable(executable)
+            args(args)
+            if (project.logger.isEnabled(LogLevel.DEBUG)) {
+                args("-vv")
+            } else if (project.logger.isEnabled(LogLevel.INFO)) {
+                args("-v")
+            }
+            if (release) {
+                args("--release")
+            }
+            args(listOf("--target", target))
+        }.assertNormalExitValue()
+    }
+}

src-tauri/gen/android/buildSrc/src/main/java/com/khj/pcdviewer/kotlin/RustPlugin.kt

@@ -0,0 +1,85 @@
+import com.android.build.api.dsl.ApplicationExtension
+import org.gradle.api.DefaultTask
+import org.gradle.api.Plugin
+import org.gradle.api.Project
+import org.gradle.kotlin.dsl.configure
+import org.gradle.kotlin.dsl.get
+
+const val TASK_GROUP = "rust"
+
+open class Config {
+    lateinit var rootDirRel: String
+}
+
+open class RustPlugin : Plugin<Project> {
+    private lateinit var config: Config
+
+    override fun apply(project: Project) = with(project) {
+        config = extensions.create("rust", Config::class.java)
+
+        val defaultAbiList = listOf("arm64-v8a", "armeabi-v7a", "x86", "x86_64");
+        val abiList = (findProperty("abiList") as? String)?.split(',') ?: defaultAbiList
+
+        val defaultArchList = listOf("arm64", "arm", "x86", "x86_64");
+        val archList = (findProperty("archList") as? String)?.split(',') ?: defaultArchList
+
+        val targetsList = (findProperty("targetList") as? String)?.split(',') ?: listOf("aarch64", "armv7", "i686", "x86_64")
+
+        extensions.configure<ApplicationExtension> {
+            @Suppress("UnstableApiUsage")
+            flavorDimensions.add("abi")
+            productFlavors {
+                create("universal") {
+                    dimension = "abi"
+                    ndk {
+                        abiFilters += abiList
+                    }
+                }
+                defaultArchList.forEachIndexed { index, arch ->
+                    create(arch) {
+                        dimension = "abi"
+                        ndk {
+                            abiFilters.add(defaultAbiList[index])
+                        }
+                    }
+                }
+            }
+        }
+
+        afterEvaluate {
+            for (profile in listOf("debug", "release")) {
+                val profileCapitalized = profile.replaceFirstChar { it.uppercase() }
+                val buildTask = tasks.maybeCreate(
+                    "rustBuildUniversal$profileCapitalized",
+                    DefaultTask::class.java
+                ).apply {
+                    group = TASK_GROUP
+                    description = "Build dynamic library in $profile mode for all targets"
+                }
+
+                tasks["mergeUniversal${profileCapitalized}JniLibFolders"].dependsOn(buildTask)
+
+                for (targetPair in targetsList.withIndex()) {
+                    val targetName = targetPair.value
+                    val targetArch = archList[targetPair.index]
+                    val targetArchCapitalized = targetArch.replaceFirstChar { it.uppercase() }
+                    val targetBuildTask = project.tasks.maybeCreate(
+                        "rustBuild$targetArchCapitalized$profileCapitalized",
+                        BuildTask::class.java
+                    ).apply {
+                        group = TASK_GROUP
+                        description = "Build dynamic library in $profile mode for $targetArch"
+                        rootDirRel = config.rootDirRel
+                        target = targetName
+                        release = profile == "release"
+                    }
+
+                    buildTask.dependsOn(targetBuildTask)
+                    tasks["merge$targetArchCapitalized${profileCapitalized}JniLibFolders"].dependsOn(
+                        targetBuildTask
+                    )
+                }
+            }
+        }
+    }
+}