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, 46 insertions, 0 deletions

diff --git a/src/cell.h b/src/cell.h
new file mode 100644
index 0000000..41b16eb
--- /dev/null
+++ b/src/cell.h
@@ -0,0 +1,46 @@
+#ifndef TERM_CELL_H
+#define TERM_CELL_H
+
+/*
+ * The cell layout that the terminal stores. Only src/term uses it. A
+ * snapshot converts these cells to the public struct term_cell.
+ */
+
+#include "term.h"
+
+enum cell_flags {
+    CELL_BOLD      = 1 << 0,
+    CELL_ITALIC    = 1 << 1,
+    CELL_UNDERLINE = 1 << 2,
+    CELL_STRIKE    = 1 << 3,
+    CELL_OVERLINE  = 1 << 4,
+    CELL_EMOJI     = 1 << 5,
+    CELL_TEXT      = 1 << 6,
+    CELL_WIDE      = 1 << 7,
+    CELL_TRAIL     = 1 << 8,
+    CELL_WRAP_PAD  = 1 << 9,
+    CELL_FAINT     = 1 << 10,
+    CELL_DOUBLE_UNDERLINE = 1 << 11,
+    CELL_CURLY_UNDERLINE  = 1 << 12,
+    CELL_DOTTED_UNDERLINE = 1 << 13,
+    CELL_DASHED_UNDERLINE = 1 << 14,
+    CELL_LINK      = 1 << 15,
+};
+
+#define CELL_ANY_UNDERLINE \
+    (CELL_UNDERLINE | CELL_DOUBLE_UNDERLINE | CELL_CURLY_UNDERLINE | \
+     CELL_DOTTED_UNDERLINE | CELL_DASHED_UNDERLINE)
+
+/* c is a code point or a grapheme handle. pad holds the OSC 8 link id. */
+struct cell {
+    uint32_t c;
+    uint32_t fg;
+    uint32_t bg;
+    uint16_t flags;
+    uint16_t pad;
+};
+
+_Static_assert(sizeof(struct cell) == 16,
+               "struct cell must stay 16 bytes (4 cells per AVX-512 register)");
+
+#endif