Slice 4: extension host + typed bus; xdg-shell/layer-shell extracted to core extensions

The kernel now names NO concrete feature. It owns: the extension host
(install/topological activate, missing-dep/cycle = startup error), the
typed Event/Filter bus (error-isolated: a throwing extension is disabled,
never the session; RAII Subscriptions), the Host API (per-extension
facade: borrows, scene layers, event catalogue, typed services), the
public RAII Listener, and a typed surface→scene-tree registry
(Host::host_surface/scene_tree_for) that replaced the untyped
wlr_surface.data convention both extensions flagged.

- ext-xdg-shell (core): toplevel/popup lifecycle, focus-on-map,
  click/tap-to-focus, pointer/touch routing incl. button+axis (the
  kernel only moves the cursor and emits — a contract-doc lie caught by
  user hands-on), interactive move/resize via pure GrabMachine (fixes
  the request-arrives-after-release race: grab requires request ∧
  button-down, release always ends it), Alt+F1 cycle,
  Ctrl+Alt+Backspace terminate (labwc's default A-Escape=Exit killed
  the dev session once — never again; see nested-run skill).
- ext-layer-shell (core): wlr-layer-shell v1 (proto v5) for external
  clients; pure doctest-hard arrangement core; fuzzel verified visually
  nested (fix: seed outputs from output_layout at activate — events-only
  tracking missed pre-activation outputs; plus a scene-node double-free).
- First protocol codegen: vendored wlr-layer-shell XML + wayland-scanner
  server-header propagated through kernel_dep; wlr.hpp grew a
  namespace→_namespace keyword fix for the generated header.
- Glossary: 'scene layer' (user-approved). New rules earned:
  parallel-wave-builds, contract-docs.
- User hands-on verified: typing, click-to-focus, drag-select, scroll,
  titlebar drag-move (slow + flick), Alt+F1, fuzzel + arrows, touch tap,
  Ctrl+Alt+Backspace. 68 doctest cases green, ASan/UBSan clean (our
  code), idle RSS ≈73 MiB.

1 files changed, 55 insertions, 0 deletions

diff --git a/packages/ext-layer-shell/tests/test_glue.cpp b/packages/ext-layer-shell/tests/test_glue.cpp
new file mode 100644
index 0000000..6a1ac16
--- /dev/null
+++ b/packages/ext-layer-shell/tests/test_glue.cpp
@@ -0,0 +1,55 @@
+#define DOCTEST_CONFIG_IMPLEMENT_WITH_MAIN
+#include <doctest/doctest.h>
+
+#include <unbox/ext-layer-shell/ext_layer_shell.hpp>
+#include <unbox/kernel/server.hpp>
+
+#include <cstdlib>
+#include <memory>
+
+// Glue tests — lenient, headless. The pure arrangement math is proven hard in
+// test_arrangement.cpp; here we only verify the extension installs, activates,
+// creates its global, drives the event loop, and shuts down cleanly under the
+// wlr headless backend (no GPU, no parent session).
+
+namespace {
+
+auto make_headless_server() -> std::unique_ptr<unbox::kernel::Server> {
+    setenv("WLR_BACKENDS", "headless", 1);
+    setenv("WLR_RENDERER", "pixman", 1);
+    setenv("WLR_HEADLESS_OUTPUTS", "1", 1);
+    return unbox::kernel::Server::create({});
+}
+
+} // namespace
+
+TEST_CASE("ext-layer-shell installs, activates, and creates its global") {
+    auto server = make_headless_server();
+    server->install(unbox::ext_layer_shell::create());
+    // Activation creates the wlr_layer_shell_v1 global on the display; a
+    // throwing activate() (e.g. create failure) would propagate here.
+    server->activate_extensions();
+    CHECK(!server->socket_name().empty());
+}
+
+TEST_CASE("ext-layer-shell dispatches and shuts down cleanly") {
+    auto server = make_headless_server();
+    server->install(unbox::ext_layer_shell::create());
+    server->activate_extensions();
+    for (int i = 0; i < 5; ++i) {
+        CHECK(server->dispatch(10));
+    }
+    // Destruction runs the full shutdown sequence; the extension's RAII members
+    // (global listener, output subscriptions, scene nodes) release in reverse
+    // declaration order with no leaked listeners.
+}
+
+TEST_CASE("ext-layer-shell activates idempotently alongside the headless output") {
+    auto server = make_headless_server();
+    server->install(unbox::ext_layer_shell::create());
+    server->activate_extensions();
+    server->activate_extensions(); // no-op second call
+    for (int i = 0; i < 3; ++i) {
+        CHECK(server->dispatch(10));
+    }
+}