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, 27 insertions, 0 deletions

diff --git a/.editorconfig b/.editorconfig
new file mode 100644
index 0000000..41f7f1b
--- /dev/null
+++ b/.editorconfig
@@ -0,0 +1,27 @@
+# ggaze editor config — mirrors docs/coding-conventions.md + .clang-format.
+root = true
+
+[*]
+charset = utf-8
+end_of_line = lf
+insert_final_newline = true
+trim_trailing_whitespace = true
+indent_style = space
+indent_size = 3
+max_line_length = 80
+
+[*.{c,h}]
+indent_size = 3
+
+[meson.build]
+indent_size = 3
+
+[*.md]
+max_line_length = off
+trim_trailing_whitespace = false
+
+[*.{yml,yaml}]
+indent_size = 2
+
+[Makefile]
+indent_style = tab
\ No newline at end of file