Replace bundled ROM extraction with runtime import/download flow

Commodore ROMs are copyrighted and can no longer ship inside the APK.
MainActivity now detects missing ROMs on first launch and blocks
startup with a dialog offering two paths: pick files via the system
file picker, or download the official VICE 3.8 tarball and extract the
four ROMs from it client-side (minimal USTAR reader, no extra deps).

- Drop the extractViceRoms Gradle task and asset bundling; add
  res/extract_roms.sh for local sideloading during development instead
- gitignore keystores/keystore.properties ahead of a signed release
- Move architecture.md into docs/, refresh it for the screen-mirroring
  and watch-input additions, and add accompanying Mermaid diagrams
- Add docs/debugging.md and docs/publish.md (Play Store release notes,
  ROM-import compliance rationale)

SchwertUndMagieOnPebbleCompanionApp/app/build.gradle.kts

@@ -130,47 +130,12 @@ tasks.whenTaskAdded {
     }
 }
 
-// ---------------------------------------------------------------------------
-// ROM extraction task
-//
-// Extracts C64 and drive ROMs from the bundled VICE tarball into the Android
-// assets directory so they are packaged into the APK automatically.
-// Output files are gitignored — the tarball is the single source of truth.
-// ---------------------------------------------------------------------------
-
-val assetsDir = layout.projectDirectory.dir("src/main/assets")
-
-tasks.register<Copy>("extractViceRoms") {
-    group = "build"
-    description = "Extract C64 and 1541 ROMs from the VICE tarball into assets/"
-
-    from(tarTree(viceTarball.asFile)) {
-        include("vice-3.8/data/C64/kernal-901227-03.bin")
-        include("vice-3.8/data/C64/basic-901226-01.bin")
-        include("vice-3.8/data/C64/chargen-901225-01.bin")
-        include("vice-3.8/data/DRIVES/dos1541-325302-01+901229-05.bin")
-        eachFile {
-            // Flatten the tarball directory structure: place each ROM directly
-            // in assets/ with its short name rather than the versioned filename.
-            relativePath = RelativePath(true, when (name) {
-                "kernal-901227-03.bin"            -> "kernal"
-                "basic-901226-01.bin"             -> "basic"
-                "chargen-901225-01.bin"           -> "chargen"
-                "dos1541-325302-01+901229-05.bin" -> "1541"
-                else -> name
-            })
-        }
-        includeEmptyDirs = false
-    }
-    into(assetsDir)
-}
-
-// Run extractViceRoms before assets are merged into the APK.
-tasks.whenTaskAdded {
-    if (name.startsWith("merge") && name.endsWith("Assets")) {
-        dependsOn("extractViceRoms")
-    }
-}
+// Note: C64/1541 ROMs are intentionally NOT bundled into the APK — they are
+// copyrighted Commodore firmware. The app prompts the user to import their
+// own ROM dump at runtime instead (see MainActivity.showRomImportDialog()).
+// res/extract_roms.sh remains available for extracting ROMs from the VICE
+// tarball locally (e.g. to sideload onto a test device), but nothing in this
+// build copies them into assets/ or the APK.
 
 dependencies {
     implementation(libs.androidx.activity.ktx)