One Layer for tags, notices, headers and bodies; a taller tag is one layer of rows; wire v8

src/Layer.zig merges TagLayer and BodyLayer. `rows` (0 = no layer) and a
cursor at {x, y}. A tag of N rows is ONE layer of N grid rows: tagHit answers
the row as `line`, bodyHit keeps its meaning, and the per-line layer bases
(TAG_LINE_LAYER_BASE, HEADER_LINE_LAYER_BASE) are gone, not aliased.

Wire v8, the one bump: tag layers carry rows and cursor y, and the frame
carries the placed region list. v7 and v9 peers are refused in both
directions (server test over both, a new frontend test over both).

web: tag_layer_value 11 = rows, 12 = cursor y; app.mjs lays every row.
macOS: the Zig side compiles against Layer; pardes.h still sees one row
per tag layer (accepted, the macOS shell is ignored for now).

No visual change: snapshot goldens and the 17 GUI goldens byte-identical.

Shared files touched: pardes.zig, Messages.zig, gui.zig, macos.zig,
detached/client.zig, detached/server.zig, detached/wire.zig (plus web.zig,
app.mjs, edit.zig, look.zig). Not touched: mouse.zig, tagline.zig,
colors.zig, tty.zig, dump.zig, exec.zig, host_io.zig, panes.zig.

1 files changed, 6 insertions, 6 deletions

diff --git a/src/macos.zig b/src/macos.zig
index fce0a53e..f7e03cd4 100644
--- a/src/macos.zig
+++ b/src/macos.zig
@@ -1861,9 +1861,9 @@ fn clearFrame(st: *State) void {
     st.panel_diff_len = 0;
 }
 
-fn blankTagCells(cells: []Cell, cols: u16, rows: u16, source: []const pardes.Cell, layers: []const pardes.TagLayer) void {
+fn blankTagCells(cells: []Cell, cols: u16, rows: u16, source: []const pardes.Cell, layers: []const pardes.Layer) void {
     for (layers) |layer| {
-        if (layer.cols == 0 or layer.viewport.y >= rows or layer.viewport.x >= cols) continue;
+        if (layer.rows == 0 or layer.viewport.y >= rows or layer.viewport.x >= cols) continue;
         const start = @as(usize, layer.viewport.y) * cols + layer.viewport.x;
         const count = @min(layer.viewport.w, cols - layer.viewport.x);
         for (cells[start..][0..count], source[start..][0..count]) |*cell, was| {
@@ -1879,7 +1879,7 @@ fn blankTagCells(cells: []Cell, cols: u16, rows: u16, source: []const pardes.Cel
 fn tagCursorCovered(core: *const pardes.Pardes) bool {
     const cursor = core.surface.cursor orelse return false;
     for (core.surface.tag_layers) |layer| {
-        if (layer.cols != 0 and cursor.y == layer.viewport.y and cursor.x >= layer.viewport.x and
+        if (layer.rows != 0 and cursor.y == layer.viewport.y and cursor.x >= layer.viewport.x and
             cursor.x - layer.viewport.x < layer.viewport.w) return true;
     }
     return false;
@@ -2121,7 +2121,7 @@ export fn pardes_tag_layer_value(index: u32, field: u32) u32 {
         5 => layer.viewport.y,
         6 => layer.viewport.w,
         7 => layer.viewport.h,
-        8 => if (layer.cursor) |c| c.col else 65535,
+        8 => if (layer.cursor) |c| c.x else 65535,
         9 => if (layer.cursor) |c| @intFromBool(c.bar) else 0,
         10 => @as(u32, layer.bg[0]) << 16 | @as(u32, layer.bg[1]) << 8 | layer.bg[2],
         11 => @intFromBool(layer.kind == .pane and st.core.settings.tag_bottom),
@@ -2139,7 +2139,7 @@ export fn pardes_tag_layer_cells(index: u32) ?[*]const Cell {
     const st = &(state orelse return null);
     if (index >= pardes.MAX_TAG_LAYERS) return null;
     const layer = &st.core.surface.tag_layers[index];
-    if (layer.cols == 0) return null;
+    if (layer.rows == 0) return null;
     const cells = &st.tag_cells[index];
     if (cells.len != layer.cells.len) cells.* = st.gpa.realloc(cells.*, layer.cells.len) catch return null;
     for (layer.cells, cells.*) |source, *out| out.* = encodeCell(source);
@@ -3110,7 +3110,7 @@ test "mac tag layer ABI preserves logical capacity and physical grip" {
     logical[11].text[0] = 'Z';
     logical[11].len = 1;
     logical[11].default = false;
-    core.surface.tag_layers[0] = .{ .kind = .pane, .id = 1, .serial = 42, .viewport = .{ .x = 2, .y = 1, .w = 6, .h = 1 }, .cols = 12, .cells = &logical, .bg = .{ 0x12, 0x34, 0x56 }, .cursor = .{ .col = 11, .bar = true } };
+    core.surface.tag_layers[0] = .{ .kind = .pane, .id = 1, .serial = 42, .viewport = .{ .x = 2, .y = 1, .w = 6, .h = 1 }, .cols = 12, .rows = 1, .cells = &logical, .bg = .{ 0x12, 0x34, 0x56 }, .cursor = .{ .x = 11, .y = 0, .bar = true } };
     defer core.surface.tag_layers[0] = .{};
     try std.testing.expectEqual(@as(u32, 12), pardes_tag_layer_value(0, 0));
     try std.testing.expectEqual(@as(u32, 0x123456), pardes_tag_layer_value(0, 10));