Simplify the public event and CPU API

Applications now need far less ceremony: hello.c is a 20-line loop that
handles REFRESH, CLOSE and QUIT and draws into the surface's own pixels.

- Fold GEOMETRY, STATE and FOCUS into one WINDOW event carrying size,
  scale and state; unchanged values send nothing.
- Guarantee REFRESH once a window has a size and after every resize,
  never at size zero.
- Merge DROP_HOVER into DROP with over/leave/data actions and give drag
  and drop actions enums.
- Keep event strings valid until the next wait and drop
  yasl_event_release; empty or failed waits report NONE.
- Replace copy-in presentation with a lent pixel buffer:
  yasl_cpu_pixels and yasl_cpu_present.
- Remove yasl_poll_event, yasl_cpu_read_pixels, unused event fields and
  comments that restated names.
- Wayland: resize floating windows in request_size instead of reporting
  it unsupported, and stop marking new GPU surfaces as Vulkan so
  yasl_vulkan_create_surface no longer fails with NATIVE_WINDOW_IN_USE.

Also includes the in-progress public API refactor that was uncommitted
in the tree (removal of the app/loop layer, new surface, GL and Vulkan
entry points).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

1 files changed, 14 insertions, 34 deletions

diff --git a/docs/api-policy.md b/docs/api-policy.md
index 3e510f3..f2f4d92 100644
--- a/docs/api-policy.md
+++ b/docs/api-policy.md
@@ -1,38 +1,18 @@
 # Public API policy
 
-YASL 0.1 is pre-release. The headers under `include/yasl/` are the public API; implementation
-headers under `src/` are private even when their symbols appear in a static
-archive. The shared library exports only declarations from public headers.
-Native backend accessors are exported only for built backends. Installation
-copies both libraries, public headers, enabled native headers, and pkg-config metadata.
+YASL is pre-release 0.1. Source and ABI compatibility are not guaranteed. Rebuild
+consumers against matching installed headers/library; do not serialize public events
+or assume their layout is a stable file/network format.
 
-There is currently no stable ABI promise and no versioned shared-library SONAME.
-Rebuild consumers against the exact headers/library pair they ship. Source and
-binary compatibility can change before 1.0. Do not assume struct layout is stable
-across releases, mix headers and binaries from different revisions, or persist
-public structs as a file/network format. The release version is declared in
-`meson.build`.
+Only installed include/yasl headers are public. The surface library exposes an
+opaque surface and one tagged event record, with direct C arguments and ordinary
+pointer/integer results. Native backend headers, geometry records, callbacks, loops,
+and drawing targets under src are private even when a static archive contains them.
+The shared library exports exactly the installed public declarations.
 
-See [migration notes](migrating.md) for window creation, portable keyboard, and
-fractional scroll API changes.
-
-API changes should keep ordinary CPU drawing usable with only `<yasl/yasl.h>`
-and the C standard library. Prefer an explicit capability and an ordinary
-unsupported result over backend names in portable application logic. Native
-rendering and handles belong in the extension headers. Avoid adding engine,
-widget, renderer, or application policy to the surface layer.
-
-Every public addition or behavior change needs:
-
-- A header contract describing arguments, result, units, lifetime, threading,
-  callback timing, and unsupported behavior where applicable.
-- An update to the guide and its backend limits when observable behavior changes.
-- A runnable example when the new workflow cannot be understood from an isolated
-  call, and meaningful regression coverage for ownership or behavior changes.
-- A check that shared exports and consumers of the installed library still work.
-
-Functions documenting errno set it on failure. Other booleans report acceptance
-or availability without a guaranteed errno; void setters are best effort.
-Callbacks and successful returns do not imply confirmed screen presentation.
-See `yasl_timing.source` for provenance. Future changes that strengthen error
-reporting must preserve these distinctions in documentation.
+Do not restore removed runner/frame/display APIs or compatibility aliases. Keep
+rendering bridges separate from the portable surface/input core and preserve the
+application's ownership of GPU resources and its loop. Public additions need clear
+units, ownership, thread/callback timing, errors and unsupported behavior, useful
+examples, and behavior coverage. Update the guide and test installed shared/static
+consumers and exports. Changes affecting Cocoa need a native macOS build/test.