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, 46 insertions, 0 deletions

diff --git a/.clang-format b/.clang-format
new file mode 100644
index 0000000..05e8ba5
--- /dev/null
+++ b/.clang-format
@@ -0,0 +1,46 @@
+---
+# ggaze .clang-format — matches docs/coding-conventions.md and the
+# c-best-practices skill. Enforced in CI with `clang-format --dry-run -Werror`.
+Language:        Cpp
+BasedOnStyle:    LLVM
+
+# 3-space indent, no tabs, 80-col limit.
+# (UseTab singular is the canonical clang-format key across LLVM >=16; the
+# older plural spelling is rejected by current toolchains.)
+ColumnLimit:     80
+IndentWidth:     3
+UseTab:          Never
+TabWidth:        3
+ContinuationIndentWidth: 3
+
+# K&R braces (opening brace on the same line).
+BreakBeforeBraces: Attach
+
+# Return type on its own line above the function name (c-best-practices).
+# AllDefinitions is accepted by both LLVM 18 (Fedora 40) and LLVM 22.
+AlwaysBreakAfterReturnType: AllDefinitions
+
+# Pointer asterisk on the variable: `Token *p_token`, not `Token* p_token`.
+PointerAlignment: Right
+
+# Keep the hand-written include order (own header, system, project).
+SortIncludes:        false
+IncludeBlocks:       Preserve
+
+# Spacing.
+SpaceBeforeParens:       ControlStatements
+SpaceAfterCStyleCast:    false
+SpacesInParentheses:     false
+SpacesInSquareBrackets:  false
+
+# No collapsing short control bodies onto one line.
+AllowShortIfStatementsOnASingleLine: Never
+AllowShortBlocksOnASingleLine:       Empty
+AllowShortFunctionsOnASingleLine:    Empty
+AllowShortLoopsOnASingleLine:        false
+AllowShortEnumsOnASingleLine:        false
+
+AlignAfterOpenBracket: Align
+AlignConsecutiveAssignments: Consecutive
+AlignConsecutiveDeclarations: Consecutive
+AlignTrailingComments: true
\ No newline at end of file