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, 8 insertions, 4 deletions

diff --git a/src/web.zig b/src/web.zig
index 532e3794..ac0ecbbf 100644
--- a/src/web.zig
+++ b/src/web.zig
@@ -224,13 +224,13 @@ export fn pardes_mouse_pixel(button_arg: u32, kind_arg: u32, col_arg: u32, row_a
     var hit: ?pardes.Mouse.BodyHit = null;
     for (&s.core.surface.body_layers) |*layer| {
         const point = source orelse break;
-        hit = layer.hitAt(point.x * bw, point.y * bh, bw, bh, tw, th);
+        hit = layer.bodyHit(point.x * bw, point.y * bh, bw, bh, tw, th);
         if (hit != null) break;
     }
     var tag_hit: ?pardes.TagHit = null;
     for (&s.core.surface.tag_layers) |*layer| {
         const point = source orelse break;
-        tag_hit = layer.hitAt(point.x * bw, point.y * bh, bw, bh, tw, th);
+        tag_hit = layer.tagHit(point.x * bw, point.y * bh, bw, bh, tw, th);
         if (tag_hit != null) break;
     }
     mouseWithHit(button_arg, kind_arg, col_arg, row_arg, mods, hit, tag_hit);
@@ -341,6 +341,7 @@ export fn pardes_tag_layer_value(index: u32, field: u32) u32 {
     const s = &(state orelse return 0);
     if (index >= pardes.MAX_TAG_LAYERS) return 0;
     const layer = &s.core.surface.tag_layers[index];
+    if (layer.rows == 0) return 0;
     return switch (field) {
         0 => layer.cols,
         1 => @intFromEnum(layer.kind),
@@ -350,9 +351,12 @@ 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],
+        // A band has a row to each line of its tag: `cols * rows` cells.
+        11 => layer.rows,
+        12 => if (layer.cursor) |c| c.y else 65535,
         else => 0,
     };
 }
@@ -361,7 +365,7 @@ export fn pardes_tag_layer_cells(index: u32) ?[*]const WebCell {
     const s = &(state orelse return null);
     if (index >= pardes.MAX_TAG_LAYERS) return null;
     const layer = &s.core.surface.tag_layers[index];
-    if (layer.cols == 0) return null;
+    if (layer.rows == 0) return null;
     const cells = &s.tag_cells[index];
     if (cells.len != layer.cells.len) cells.* = gpa.realloc(cells.*, layer.cells.len) catch return null;
     for (layer.cells, cells.*) |source, *out| out.* = encodeWebCell(source);