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.

5 files changed, 74 insertions, 0 deletions

diff --git a/tests/fixtures/.gitkeep b/tests/fixtures/.gitkeep
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/tests/fixtures/.gitkeep
diff --git a/tests/helpers/.gitkeep b/tests/helpers/.gitkeep
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/tests/helpers/.gitkeep
diff --git a/tests/integration/meson.build b/tests/integration/meson.build
new file mode 100644
index 0000000..5d540a0
--- /dev/null
+++ b/tests/integration/meson.build
@@ -0,0 +1,3 @@
+# Integration tests (cross-module flows, real temp dirs, offscreen GTK).
+# Empty in Phase 0 — suites land with the milestones that first make each
+# flow possible; see docs/IMPLEMENTATION.md "Planned integration suites".
\ No newline at end of file
diff --git a/tests/meson.build b/tests/meson.build
new file mode 100644
index 0000000..c0ec9fb
--- /dev/null
+++ b/tests/meson.build
@@ -0,0 +1,22 @@
+# ggaze tests — two tracks (see docs/IMPLEMENTATION.md "Two test tracks").
+#
+#   unit        plain-C module tests, no display needed (>=80% coverage gate,
+#               warn until M10 then fail).
+#   integration  cross-module flows with real temp dirs + offscreen GTK.
+#
+# Run one track:   meson test -C build --suite unit
+#                  meson test -C build --suite integration
+# Coverage:        meson setup -Db_coverage=true build
+#                  meson test -C build
+#                  ninja -C build coverage   (needs lcov + genhtml)
+
+test_bootstrap = executable(
+   'test_bootstrap',
+   ['test_bootstrap.c', ggaze_conf_h],
+   include_directories : inc,
+   dependencies : [glib_dep],
+   install : false,
+)
+test('bootstrap', test_bootstrap, suite : 'unit')
+
+subdir('integration')
\ No newline at end of file
diff --git a/tests/test_bootstrap.c b/tests/test_bootstrap.c
new file mode 100644
index 0000000..fea0443
--- /dev/null
+++ b/tests/test_bootstrap.c
@@ -0,0 +1,49 @@
+/*:*
+ * ggaze — bootstrap sanity test
+ *
+ * Confirms the build/test harness is wired: g_test_init runs, and the
+ * generated ggaze-config.h exposes the app id and version. No display,
+ * no GTK — this is the smallest proof that the unit-test track compiles
+ * and executes under `meson test --suite unit`.
+ *
+ * Copyright (c) 2026 ggaze contributors
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ *:*/
+
+#include "ggaze-config.h"
+
+#include <glib.h>
+#include <string.h>
+
+static void
+test_app_id(void) {
+   g_assert_cmpstr(GGAZE_APP_ID, ==, "org.buetow.ggaze");
+}
+
+static void
+test_version(void) {
+   g_assert_cmpstr(GGAZE_VERSION, !=, NULL);
+   g_assert_cmpint((int)strlen(GGAZE_VERSION), >, 0);
+}
+
+static void
+test_feature_flags_are_binary(void) {
+   /* Feature flags must be 0 or 1, never undefined (compile-time guard). */
+   g_assert_cmpint(GGAZE_HAVE_GEGL, >=, 0);
+   g_assert_cmpint(GGAZE_HAVE_GEGL, <=, 1);
+   g_assert_cmpint(GGAZE_HAVE_JXL, >=, 0);
+   g_assert_cmpint(GGAZE_HAVE_JXL, <=, 1);
+   g_assert_cmpint(GGAZE_HAVE_AVIF, >=, 0);
+   g_assert_cmpint(GGAZE_HAVE_AVIF, <=, 1);
+   g_assert_cmpint(GGAZE_HAVE_HEIF, >=, 0);
+   g_assert_cmpint(GGAZE_HAVE_HEIF, <=, 1);
+}
+
+int
+main(int i_argc, char **c_argv) {
+   g_test_init(&i_argc, &c_argv, NULL);
+   g_test_add_func("/bootstrap/app_id", test_app_id);
+   g_test_add_func("/bootstrap/version", test_version);
+   g_test_add_func("/bootstrap/feature_flags", test_feature_flags_are_binary);
+   return (g_test_run());
+}
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