bundling: Android APK pipeline moved into sx; android.sx state-on-plat

Week 7 of /Users/agra/.claude/plans/lets-plan-to-move-splendid-pumpkin.md
plus the android.sx refactor + three sx-compiler fixes hit along the way
to get chess on Pixel 7 Pro responding to touch end-to-end.

library/modules/platform/bundle.sx now covers the Android APK shape
alongside macOS / iOS-sim / iOS-device. `android_bundle_main` discovers
the SDK ($ANDROID_HOME / $ANDROID_SDK_ROOT / $HOME/Library/Android/sdk),
picks the highest-versioned build-tools + platforms via
`process.run("ls .. | sort -V | tail -1")`, stages
`<apk>.stage/lib/arm64-v8a/<libfoo.so>`, synthesizes
AndroidManifest.xml (NativeActivity vs `#jni_main` Activity branch),
writes each `#jni_main` decl's Java source under
`<stage>/java/<pkg>/<Cls>.java`, runs javac --release 11 + d8 to
produce classes.dex, aapt2-links the unaligned APK, appends lib/ +
classes.dex + each registered asset tree via zip, zipalign + ensure
debug keystore via keytool + apksigner sign.

Compiler-side accessors (src/ir/compiler_hooks.zig + library/modules/compiler.sx):
- is_android predicate.
- set_manifest_path / manifest_path + set_keystore_path / keystore_path.
- jni_main_count / jni_main_foreign_path_at(i) /
  jni_main_java_source_at(i) surface the `#jni_main` emissions that
  the Zig createApk previously consumed directly.
- main.zig wires manifest_path, keystore_path, and the per-decl
  (foreign_path, java_source) parallel slices into BuildConfig before
  invoking the post-link callback.

CLI `--apk <path>` keeps working as a transitional alias: it now feeds
bundle_path so the existing auto-`post_link_module = "platform.bundle"`
shim fires the same way as `--bundle`. main.zig no longer calls
target.createApk directly.

Deletions in src/target.zig: createApk, compileJniMainSources,
buildJniMainManifest, buildAndroidManifest, ensureDebugKeystore,
libNameFromSoBasename, plus helpers splitForeignPath / discoverJavac /
discoverAndroidSdk / findHighestSubdir / runProcess / runProcessIn
(~400 lines). git grep returns only the obituary comment.

library/modules/platform/android.sx refactor (chess Android dependency):
- Module-level globals retired (g_app_window, g_egl_*, g_viewport_*,
  g_dpi_scale, g_should_stop, g_render_thread*, g_user_main_fn,
  g_touch_*) → AndroidPlatform struct fields.
- All sx_android_* helpers take `plat: *AndroidPlatform` as first arg.
  Render thread receives plat via pthread_create's arg.
- New `logical_w: f32 = 0.0` field. Consumers set it before init() to
  define the design width in points; `recompute_scale` derives
  `dpi_scale = pixel_w / logical_w` (or 1.0 if unset). Called on
  init / set_viewport / egl_init. drain_touches divides incoming
  physical pixel coords by dpi_scale so chess sees logical-space
  positions matching its layout. Touch lands on the right squares.

Three sx-compiler bugs hit + fixed along the way:

1. Top-level `inline if OS == .X { decls }` body decls were silently
   dropped because scanDecls/lowerDecls had no .if_expr arm. New
   `flattenComptimeConditionals` pre-pass in src/imports.zig
   (threaded via ComptimeContext from core.zig) hoists matching arms
   recursively. Regression at examples/124-inline-if-hoist-toplevel.sx.

2. Parser rejected `#import` / `#framework` inside inline-if bodies
   because parseStmt in src/parser.zig only had arms for `#insert`.
   Added the missing arms. Regression at
   examples/123-inline-if-import-in-body.sx (landed earlier).

3. JNI `Call<T>Method` switches in src/ir/emit_llvm.zig (instance /
   nonvirtual / static) were missing `.f32` rows — jfloat returns
   (e.g. MotionEvent.getX/getY) fell into the silent-undef else arm.
   Chess's sx_android_push_touch(plat, getAction(), getX(), getY())
   delivered garbage f32 coords to the touch ring, so taps landed
   nowhere recognisable. Added `.f32 => Jni.Call{Static,Nonvirtual,}FloatMethod`
   rows to all three switches; lifted unsupported-type detection
   from emit_llvm into lowerForeignMethodCall with proper
   source-spanned diagnostics (`isJniReturnTypeSupported`). Regressions
   at examples/ffi-jni-call-10-jfloat-return.sx,
   examples/ffi-jni-class-09-multi-float-args.sx,
   examples/ffi-jni-call-11-unsupported-return-diag.sx.

Stale-snapshot drift in tests/expected/ffi-objc-call-03-selector-sharing.ir
and ffi-objc-call-06-sret-return.ir picks up the new BuildOptions
accessor extern decls (is_android, set_manifest_path,
set_keystore_path, jni_main_count, jni_main_foreign_path_at,
jni_main_java_source_at). Verified diff is dead-decl-only.

Chess on Pixel 7 Pro: tap on e2 white pawn -> yellow selection +
green dots on legal e3/e4 targets; tap on e4 -> board updates with
1. e4, "Black to move" + "1. e4" in info panel.

zig build && zig build test && bash tests/run_examples.sh -> 145/145
green. bash tests/cross_compile.sh -> 7/7 green.

src/ir/lower.zig

@@ -4150,6 +4150,19 @@ pub const Lowering = struct {
 
         const ret_ty = if (method.return_type) |rt| self.resolveType(rt) else .void;
 
+        // Reject return types the JNI emit path can't dispatch — emit_llvm's
+        // Call<T>Method switch only covers void / bool / s32 / s64 / f32 / f64
+        // / pointer-returning. Anything else (s8 / s16 / u8 / u16 / aggregates)
+        // would silently lower to LLVMGetUndef and produce wrong arguments at
+        // the call site (chess Android touch shipped broken because s32→s32+
+        // f32 returns hit the undef path before .f32 was wired up).
+        if (!isJniReturnTypeSupported(&self.module.types, ret_ty)) {
+            if (self.diagnostics) |d| {
+                d.addFmt(.err, span, "JNI method '{s}.{s}' returns '{s}', which isn't supported by the JNI call-method lowering yet — only void/bool/s32/s64/f32/f64 and pointers are wired up", .{ fcd.name, method.name, self.module.types.typeName(ret_ty) });
+            }
+            return Ref.none;
+        }
+
         const cache_key: inst_mod.CacheKey = .{
             .name_str = method_name,
             .sig_str = desc_str,
@@ -10295,6 +10308,23 @@ fn jniMapParamType(self: *Lowering, type_node: *ast.Node) TypeId {
     return self.resolveType(type_node);
 }
 
+/// Whether emit_llvm's `jni_msg_send` lowering can dispatch a Call<T>Method
+/// for this return type. Anything outside this set falls into the `else`
+/// arm of the switches in `emit_llvm.zig` and would silently produce
+/// `LLVMGetUndef` — a footgun that previously shipped (chess Android touch
+/// went undef because `MotionEvent.getX() -> f32` wasn't in the switch).
+/// Pointer-typed returns route through `CallObjectMethod`.
+pub fn isJniReturnTypeSupported(table: *const @import("types.zig").TypeTable, ret_ty: TypeId) bool {
+    return switch (ret_ty) {
+        .void, .bool, .s32, .s64, .f32, .f64 => true,
+        else => blk: {
+            if (ret_ty.isBuiltin()) break :blk false;
+            const info = table.get(ret_ty);
+            break :blk info == .pointer or info == .many_pointer;
+        },
+    };
+}
+
 /// Encode a (foreign_path, method_name) pair as the JNI-resolved symbol
 /// `Java_<pkg-mangled>_<Class>_sx_1<method-mangled>`. JNI mangling:
 /// `/` → `_`, `_` → `_1`. The `sx_` prefix matches the Java-side