term: move the term core to subprojects/term

The core now builds, tests, and benchmarks alone, as a Meson subproject
with no dependency on the main tree.

- include/term/ holds term.h and the header-only unicode/. src/ holds
  the core and its private headers. The main tree gets only
  include/term through term_dep, so it cannot reach a private header.
- The term tests, the term benchmarks, the Kitty parser suite, and
  tools/amalgamate.py and tools/generate_unicode.py move with it. The
  tests run as term:<name>.
- The main build passes its -march (arch_flag) and b_ndebug to the
  subproject. A directory configured before this commit needs
  meson configure -Dterm:arch_flag=-march=... once.
- The term tests compile with -UNDEBUG. They do work inside assert.
- The subproject exports term_test_dep with term_api.h, for the main
  tree's render, thumbnail, color, and selection tests.
- The Kitty bridge used struct vector2i and has not compiled since the
  public API redesign. It builds again. 2 of its 14 tests fail: REP
  after a tab, and a cursor report after a resize.
- dirgraph.py drops the term and unicode layers. Its self-test uses pty.
- The symbols test ignores the __odr_asan symbols that ASan adds.

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

1 files changed, 16 insertions, 0 deletions

diff --git a/tests/header_test.sh b/tests/header_test.sh
new file mode 100644
index 0000000..6636418
--- /dev/null
+++ b/tests/header_test.sh
@@ -0,0 +1,16 @@
+#!/usr/bin/env bash
+# A host includes term.h and nothing else. The header compiles alone as
+# strict C11 and as C++, with only include/term on the include path.
+set -euo pipefail
+cd "${1:-$(dirname "$0")/..}"
+cc=${CC:-cc}
+cxx=${CXX:-c++}
+
+status=0
+echo '#include "term.h"' | "$cc" -std=c11 -Wall -Wextra -Wpedantic -Werror \
+    -Iinclude/term -x c -fsyntax-only - || { echo "term.h: not valid C11" >&2; status=1; }
+if command -v "$cxx" >/dev/null; then
+    echo '#include "term.h"' | "$cxx" -std=c++17 -Wall -Wextra -Wpedantic -Werror \
+        -Iinclude/term -x c++ -fsyntax-only - || { echo "term.h: not valid C++" >&2; status=1; }
+fi
+exit $status