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, 7 insertions, 80 deletions

diff --git a/src/tag_layer.zig b/src/tag_layer.zig
index 7cfe5bbf..213ebc07 100644
--- a/src/tag_layer.zig
+++ b/src/tag_layer.zig
@@ -1,83 +1,10 @@
-//! Tag text has its own horizontal pitch. Its viewport stays in physical
-//! body-grid coordinates so compact text never changes pane hit targets.
+//! Pointer hits on tag bands (Layer.TagHit): comparing two, and bringing one
+//! that left its band back onto it.
 const std = @import("std");
 const pardes = @import("pardes.zig");
-
-/// `notice` is a pane's transient line -- a builtin's name, a pending leader
-/// chord -- carried as a tagline-shaped band so it gets the tagline's height,
-/// small-font metrics, band offset and border instead of being a body-grid row
-/// wearing a tagline font.
-pub const Kind = enum(u8) { workspace, column, pane, notice };
-pub const Hit = struct {
-    kind: Kind,
-    id: u16,
-    serial: u32,
-    col: u16,
-    /// Which line of a taller tag the layer draws.
-    line: u16 = 0,
-    pixel_x: f32,
-    pixel_y: f32,
-    metrics: pardes.RowMetrics,
-};
-pub const Layer = struct {
-    kind: Kind = .workspace,
-    id: u16 = 0,
-    serial: u32 = 0,
-    /// A pane's tag taller than a line is drawn a layer to a line; this is
-    /// which one, counted from its first.
-    line: u16 = 0,
-    viewport: pardes.Rect = .{ .x = 0, .y = 0, .w = 0, .h = 0 },
-    cols: u16 = 0,
-    bg: [3]u8 = .{ 0, 0, 0 },
-    cells: []pardes.Cell = &.{},
-    cursor: ?struct { col: u16, bar: bool = false } = null,
-    /// Vertical offset in rows (negative: above its viewport), for a band
-    /// that is moving into place. A pixel shell draws it offset and clipped
-    /// to the rows below the viewport's top; the grid has no such thing.
-    slide: f32 = 0,
-    /// How present a notice band is (1 = fully) while it fades up or
-    /// dissolves. `bg` and the cells are already blended by it; a pixel
-    /// shell uses it for what it draws around the band, like its rule.
-    fade: f32 = 1,
-
-    pub fn capacity(layer: *const Layer, metrics: pardes.RowMetrics) u16 {
-        return @intCast(@min(std.math.maxInt(u16), @max(1, @as(u32, layer.viewport.w) * @max(1, metrics.body_w) / @max(1, metrics.tagline_w))));
-    }
-
-    pub fn hitAt(layer: *const Layer, x: f32, y: f32, body_w: f32, body_h: f32, tagline_w: f32, tagline_h: f32) ?Hit {
-        if (layer.cols == 0 or !std.math.isFinite(x) or !std.math.isFinite(y)) return null;
-        for ([_]f32{ body_w, body_h, tagline_w, tagline_h }) |metric|
-            if (!std.math.isFinite(metric) or metric < 1 or metric > std.math.maxInt(u16)) return null;
-        const bw = @max(1, body_w);
-        const bh = @max(1, body_h);
-        const tw = std.math.clamp(tagline_w, 1, bw);
-        const th = std.math.clamp(tagline_h, 1, bh);
-        const dx = x - @as(f32, @floatFromInt(layer.viewport.x)) * bw;
-        const dy = y - @as(f32, @floatFromInt(layer.viewport.y)) * bh;
-        if (dx < 0 or dy < 0 or dx >= @as(f32, @floatFromInt(layer.viewport.w)) * bw or dy >= @as(f32, @floatFromInt(layer.viewport.h)) * bh) return null;
-        return .{
-            .kind = layer.kind,
-            .id = layer.id,
-            .serial = layer.serial,
-            .line = layer.line,
-            .col = @intFromFloat(@min(@as(f32, @floatFromInt(layer.cols - 1)), @floor(dx / tw))),
-            .pixel_x = x,
-            .pixel_y = y,
-            .metrics = .{ .body_w = @intFromFloat(bw), .body_h = @intFromFloat(bh), .tagline_w = @intFromFloat(tw), .tagline_h = @intFromFloat(th) },
-        };
-    }
-};
-
-test "tag text capacity uses its own pitch and excludes the physical grip" {
-    const layer: Layer = .{ .kind = .pane, .id = 2, .serial = 7, .viewport = .{ .x = 12, .y = 4, .w = 38, .h = 1 }, .cols = 90 };
-    try std.testing.expectEqual(@as(u16, 63), layer.capacity(.{ .body_w = 10, .tagline_w = 6 }));
-    try std.testing.expect(layer.hitAt(119.99, 85, 10, 20, 6, 12) == null);
-    try std.testing.expectEqual(@as(u16, 0), layer.hitAt(120, 85, 10, 20, 6, 12).?.col);
-    try std.testing.expectEqual(@as(u16, 50), layer.hitAt(423, 85, 10, 20, 6, 12).?.col);
-    try std.testing.expect(layer.hitAt(500, 85, 10, 20, 6, 12) == null);
-    try std.testing.expect(layer.hitAt(120, 85, std.math.nan(f32), 20, 6, 12) == null);
-    try std.testing.expect(layer.hitAt(120, 85, 10, 20, 0, 12) == null);
-}
+const Layer = @import("Layer.zig");
+const Hit = Layer.TagHit;
+const Kind = Layer.Kind;
 
 /// Whether two pointer hits name the same cell of the same tag line.
 pub fn sameCell(a: ?Hit, b: ?Hit) bool {
@@ -92,13 +19,13 @@ pub fn columnAt(p: *const pardes.Pardes, kind: Kind, id: usize, supplied: ?Hit,
     var point = supplied orelse return null;
     if (point.kind != kind or point.id != id) return null;
     if (clamp) for (p.surface.tagLayers()) |*layer| {
-        if (layer.cols == 0 or layer.kind != kind or layer.id != id or layer.serial != point.serial or layer.line != line) continue;
+        if (layer.rows == 0 or layer.kind != kind or layer.id != id or layer.serial != point.serial or line >= layer.rows) continue;
         const bw: f32 = @floatFromInt(point.metrics.body_w);
         const bh: f32 = @floatFromInt(point.metrics.body_h);
         const left = @as(f32, @floatFromInt(layer.viewport.x)) * bw;
         const right = @as(f32, @floatFromInt(layer.viewport.x + layer.viewport.w)) * bw;
         point.pixel_x = std.math.clamp(point.pixel_x, left, @max(left, right - 0.001));
-        point.pixel_y = (@as(f32, @floatFromInt(layer.viewport.y)) + 0.5) * bh;
+        point.pixel_y = (@as(f32, @floatFromInt(layer.viewport.y + line)) + 0.5) * bh;
         break;
     };
     return if (p.reprojectTagHit(point)) |mapped| mapped.col else null;