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, 0 insertions, 190 deletions

diff --git a/packages/kernel/src/toplevel.cpp b/packages/kernel/src/toplevel.cpp
deleted file mode 100644
index 150870d..0000000
--- a/packages/kernel/src/toplevel.cpp
+++ /dev/null
@@ -1,190 +0,0 @@
-#include "server_impl.hpp"
-
-#include <algorithm>
-
-namespace unbox::kernel {
-
-// ---- Focus ------------------------------------------------------------------
-
-void Server::Impl::focus_toplevel(Toplevel* toplevel) {
-    // Keyboard focus only (pointer focus follows the cursor).
-    if (toplevel == nullptr) {
-        return;
-    }
-    wlr_surface* surface = toplevel->xdg_toplevel->base->surface;
-    wlr_surface* prev_surface = seat->keyboard_state.focused_surface;
-    if (prev_surface == surface) {
-        return;
-    }
-    if (prev_surface != nullptr) {
-        // Deactivate the previously focused toplevel (client stops drawing
-        // its focused decoration state, e.g. hides the caret).
-        wlr_xdg_toplevel* prev = wlr_xdg_toplevel_try_from_wlr_surface(prev_surface);
-        if (prev != nullptr) {
-            wlr_xdg_toplevel_set_activated(prev, false);
-        }
-    }
-
-    wlr_scene_node_raise_to_top(&toplevel->scene_tree->node);
-    auto it = std::find(mapped_toplevels.begin(), mapped_toplevels.end(), toplevel);
-    if (it != mapped_toplevels.end()) {
-        mapped_toplevels.splice(mapped_toplevels.begin(), mapped_toplevels, it);
-    }
-    wlr_xdg_toplevel_set_activated(toplevel->xdg_toplevel, true);
-
-    // The seat tracks the focused surface and routes key events to it.
-    if (wlr_keyboard* keyboard = wlr_seat_get_keyboard(seat)) {
-        wlr_seat_keyboard_notify_enter(seat, surface, keyboard->keycodes,
-                                       keyboard->num_keycodes, &keyboard->modifiers);
-    }
-}
-
-auto Server::Impl::toplevel_at(double lx, double ly, wlr_surface** surface, double* sx, double* sy)
-    -> Toplevel* {
-    // Topmost scene node at the given layout coords; we only care about
-    // buffer nodes belonging to a surface tree rooted at a Toplevel.
-    wlr_scene_node* node = wlr_scene_node_at(&scene->tree.node, lx, ly, sx, sy);
-    if (node == nullptr || node->type != WLR_SCENE_NODE_BUFFER) {
-        return nullptr;
-    }
-    wlr_scene_buffer* scene_buffer = wlr_scene_buffer_from_node(node);
-    wlr_scene_surface* scene_surface = wlr_scene_surface_try_from_buffer(scene_buffer);
-    if (scene_surface == nullptr) {
-        return nullptr;
-    }
-    *surface = scene_surface->surface;
-
-    // Walk up to the tree whose data field we set: the Toplevel root.
-    wlr_scene_tree* tree = node->parent;
-    while (tree != nullptr && tree->node.data == nullptr) {
-        tree = tree->node.parent;
-    }
-    if (tree == nullptr) {
-        return nullptr;
-    }
-    return static_cast<Toplevel*>(tree->node.data);
-}
-
-// ---- Interactive move/resize grabs -------------------------------------------
-
-void Server::Impl::reset_cursor_mode() {
-    cursor_mode = CursorMode::Passthrough;
-    grabbed_toplevel = nullptr;
-}
-
-void Server::Impl::begin_interactive(Toplevel* toplevel, CursorMode mode, std::uint32_t edges) {
-    // The compositor consumes pointer events itself during a grab instead
-    // of forwarding them. (tinywl note kept: a fuller compositor would
-    // verify this against a recent button-press serial.)
-    grabbed_toplevel = toplevel;
-    cursor_mode = mode;
-
-    if (mode == CursorMode::Move) {
-        grab_x = cursor->x - toplevel->scene_tree->node.x;
-        grab_y = cursor->y - toplevel->scene_tree->node.y;
-    } else {
-        wlr_box* geo_box = &toplevel->xdg_toplevel->base->geometry;
-        const double border_x = (toplevel->scene_tree->node.x + geo_box->x) +
-                                ((edges & WLR_EDGE_RIGHT) != 0 ? geo_box->width : 0);
-        const double border_y = (toplevel->scene_tree->node.y + geo_box->y) +
-                                ((edges & WLR_EDGE_BOTTOM) != 0 ? geo_box->height : 0);
-        grab_x = cursor->x - border_x;
-        grab_y = cursor->y - border_y;
-
-        grab_geobox = *geo_box;
-        grab_geobox.x += toplevel->scene_tree->node.x;
-        grab_geobox.y += toplevel->scene_tree->node.y;
-        resize_edges = edges;
-    }
-}
-
-// ---- xdg-shell toplevels ------------------------------------------------------
-
-void Server::Impl::handle_new_toplevel(wlr_xdg_toplevel* xdg_toplevel) {
-    auto owned = std::make_unique<Toplevel>();
-    Toplevel* toplevel = owned.get();
-    toplevel->server = this;
-    toplevel->xdg_toplevel = xdg_toplevel;
-    toplevel->scene_tree = wlr_scene_xdg_surface_create(&scene->tree, xdg_toplevel->base);
-    toplevel->scene_tree->node.data = toplevel;
-    // Popups look this up to find their parent's scene tree.
-    xdg_toplevel->base->data = toplevel->scene_tree;
-    toplevels.emplace(xdg_toplevel, std::move(owned));
-
-    toplevel->map.connect(xdg_toplevel->base->surface->events.map, [this, toplevel](void*) {
-        mapped_toplevels.push_front(toplevel);
-        focus_toplevel(toplevel);
-        wlr_log(WLR_INFO, "toplevel mapped: %s",
-                toplevel->xdg_toplevel->title != nullptr ? toplevel->xdg_toplevel->title : "?");
-    });
-    toplevel->unmap.connect(xdg_toplevel->base->surface->events.unmap, [this, toplevel](void*) {
-        if (toplevel == grabbed_toplevel) {
-            reset_cursor_mode();
-        }
-        mapped_toplevels.remove(toplevel);
-    });
-    toplevel->commit.connect(xdg_toplevel->base->surface->events.commit, [toplevel](void*) {
-        if (toplevel->xdg_toplevel->base->initial_commit) {
-            // Reply to the initial commit with a 0x0 configure: the client
-            // picks its own dimensions.
-            wlr_xdg_toplevel_set_size(toplevel->xdg_toplevel, 0, 0);
-        }
-    });
-    toplevel->destroy.connect(xdg_toplevel->events.destroy, [this, toplevel](void*) {
-        // Last action: destroys `toplevel` (and these listeners with it).
-        toplevels.erase(toplevel->xdg_toplevel);
-    });
-
-    toplevel->request_move.connect(xdg_toplevel->events.request_move, [this, toplevel](void*) {
-        begin_interactive(toplevel, CursorMode::Move, 0);
-    });
-    toplevel->request_resize.connect(
-        xdg_toplevel->events.request_resize, [this, toplevel](void* data) {
-            const auto* event = static_cast<wlr_xdg_toplevel_resize_event*>(data);
-            begin_interactive(toplevel, CursorMode::Resize, event->edges);
-        });
-    toplevel->request_maximize.connect(
-        xdg_toplevel->events.request_maximize, [toplevel](void*) {
-            // Unsupported, but xdg-shell demands a configure reply.
-            if (toplevel->xdg_toplevel->base->initialized) {
-                wlr_xdg_surface_schedule_configure(toplevel->xdg_toplevel->base);
-            }
-        });
-    toplevel->request_fullscreen.connect(
-        xdg_toplevel->events.request_fullscreen, [toplevel](void*) {
-            if (toplevel->xdg_toplevel->base->initialized) {
-                wlr_xdg_surface_schedule_configure(toplevel->xdg_toplevel->base);
-            }
-        });
-}
-
-// ---- xdg-shell popups ----------------------------------------------------------
-
-void Server::Impl::handle_new_popup(wlr_xdg_popup* xdg_popup) {
-    auto owned = std::make_unique<Popup>();
-    Popup* popup = owned.get();
-    popup->xdg_popup = xdg_popup;
-    popups.emplace(xdg_popup, std::move(owned));
-
-    // Parent's scene tree was stashed in base->data when it was created
-    // (toplevel or ancestor popup).
-    wlr_xdg_surface* parent = wlr_xdg_surface_try_from_wlr_surface(xdg_popup->parent);
-    if (parent != nullptr && parent->data != nullptr) {
-        auto* parent_tree = static_cast<wlr_scene_tree*>(parent->data);
-        xdg_popup->base->data = wlr_scene_xdg_surface_create(parent_tree, xdg_popup->base);
-    }
-
-    popup->commit.connect(xdg_popup->base->surface->events.commit, [popup](void*) {
-        if (popup->xdg_popup->base->initial_commit) {
-            // A fuller compositor would also unconstrain the popup to keep
-            // it on-screen here.
-            wlr_xdg_surface_schedule_configure(popup->xdg_popup->base);
-        }
-    });
-    popup->destroy.connect(xdg_popup->events.destroy, [this, popup](void*) {
-        // Last action: destroys `popup` (and these listeners with it).
-        popups.erase(popup->xdg_popup);
-    });
-}
-
-} // namespace unbox::kernel