bootstrap: meson build, test harness, CI, conventions, README/AGENTS (et0)

Phase 0 (task et0): lays the build/test/CI/convention groundwork before any
feature code.

- meson.build: project ggaze C11 -Wall -Wextra; deps gtk4/glib/gio/libadwaita;
  feature options gegl/jxl/avif/heif (auto); generated ggaze-config.h with
  app id, version, GGAZE_HAVE_* feature flags.
- tests: GLib g_test harness with separate unit/integration suites
  (--suite unit / --suite integration); test_bootstrap sanity test proves
  the harness compiles and the config header is reachable; -Db_coverage=true
  coverage target wired.
- CI: .woodpecker/ci.yml three lanes (minimal, gegl, asan) with xvfb for the
  integration track and a coverage lane that warns until M10.
- conventions: .clang-format (3-space, 80-col, K&R, *-on-var, return type on
  its own line) + .editorconfig matching docs/coding-conventions.md; CI
  clang-format --dry-run -Werror gate.
- top-level README.md (humans) and AGENTS.md (agents) pointing into docs/.
- LICENSE (GPL-3.0-or-later), .gitignore, dir placeholders.

Acceptance: meson setup build && ninja -C build && meson test -C build green;
clang-format --dry-run --Werror clean.

1 files changed, 51 insertions, 0 deletions

diff --git a/meson.build b/meson.build
new file mode 100644
index 0000000..4c67730
--- /dev/null
+++ b/meson.build
@@ -0,0 +1,51 @@
+# ggaze — GNOME Gaze
+#
+# A small, fast, native image viewer for Fedora Linux, written in C with
+# GTK4. Full design lives in docs/; this file is the build root. Phase 0
+# establishes the build/test/CI/convention harness — no production sources
+# yet (they arrive from M0; see docs/roadmap.md).
+
+project('ggaze', 'c',
+   version : '0.1.0',
+   license : 'GPL-3.0-or-later',
+   meson_version : '>= 1.1',
+   default_options : [
+      'warning_level=2',   # -Wall -Wextra
+      'c_std=c11',
+      'b_pie=true',
+   ],
+)
+
+# --- Always-required dependencies (the core viewer needs all of these) ---
+gtk4_dep    = dependency('gtk4')
+glib_dep    = dependency('glib-2.0')
+gio_dep     = dependency('gio-2.0')
+adwaita_dep = dependency('libadwaita-1')
+
+# --- Optional backends (feature: auto/disabled/enabled). See meson_options.txt.
+gegl_dep = dependency('gegl-0.4', required : get_option('gegl'))
+jxl_dep  = dependency('libjxl',   required : get_option('jxl'))
+avif_dep = dependency('libavif', required : get_option('avif'))
+heif_dep = dependency('libheif',  required : get_option('heif'))
+
+# --- Generated config header (app id, version, feature flags) ---
+conf = configuration_data()
+conf.set_quoted('GGAZE_VERSION', meson.project_version())
+conf.set_quoted('GGAZE_APP_ID', 'org.buetow.ggaze')
+conf.set('GGAZE_HAVE_GEGL', gegl_dep.found() ? 1 : 0)
+conf.set('GGAZE_HAVE_JXL',  jxl_dep.found()  ? 1 : 0)
+conf.set('GGAZE_HAVE_AVIF', avif_dep.found() ? 1 : 0)
+conf.set('GGAZE_HAVE_HEIF', heif_dep.found() ? 1 : 0)
+
+ggaze_conf_h = configure_file(
+   input         : 'ggaze-config.h.in',
+   output        : 'ggaze-config.h',
+   configuration : conf,
+)
+
+# Include path: source root (generated header lands in the build root, which
+# meson adds automatically for targets that list ggaze_conf_h as a source).
+inc = include_directories('.')
+
+subdir('src')
+subdir('tests')
\ No newline at end of file