acme looks like acme; every theme gets acme's button, scroll column and 2px rules

acme takes plan9port's own colours (acme.c iconinit, draw.h): selections
#eeee9e in the body and #9eeeee in the tag, black ink; exec and look sweeps
#aa0000 and #006600, white ink; a #99994c scrollbar under a #ffffea thumb;
black rules; a #8888cc tag/body rule and column button.

Every theme: the grip is acme's button, its tag row's full height, in one
scroll column with the scrollbar (rail_px, 12 at a 17px tagline, scaled,
times GripWidth, a percent, default 150; same x0/x1 to the pixel):
focused clean = solid box; focused dirty = box_dirty filled to a box ring
(acme's modbutton); unfocused clean = a box_border ring round the tag's
ground; unfocused dirty = box_dirty a pixel inside that ring. The grid, which
has no ring, marks dirty with a bold * on box_dirty in the grip's second cell
and fills an unfocused grip halfway to its ring. Regions carry a dirty flag.
Column buttons are the same shape, solid. 2px rules between columns and
stacked panes (inside the tag band's slack), none at the window edge; a 1px
tag/body rule halfway between tag and page.

Theme data: tag_sel_bg, sweep_bg/fg, tag_rule, rule_px, rail_px, box_border,
box_dirty. Chrome: rule_px, tag_rule, rail_px, grip_border, grip_focus_ring;
a comptime guard on Chrome's layout forces a wire bump once v8 ships.
Structural rules are exempt from the focus-indicator rule (docs/effects.md).

Tests: acme widths; stacked rule in the slack at two tagline sizes; every
grip-column pixel is band, button, ring or rule, and the button shares the
scrollbar's x0/x1 (4 metrics x top/bottom x focus x dirty); the four grip
states distinct in every native theme with a non-colour dirty cue in the
grid; wire round-trip of the new fields.

Shared files: src/colors.zig, src/surface.zig, src/body_layer.zig,
src/tagline.zig, src/detached/wire.zig, docs/themes.md, docs/config.md,
docs/effects.md, 21 snapshot goldens (the grip cells only),
test/gui-goldens.txt.

Motion flavours differ by design, and drive notice drops and pane moves

1 files changed, 5 insertions, 5 deletions

diff --git a/test/snapshots/lspcomplete.golden b/test/snapshots/lspcomplete.golden
index 8efa7edf..0a58a231 100644
--- a/test/snapshots/lspcomplete.golden
+++ b/test/snapshots/lspcomplete.golden
@@ -16,7 +16,7 @@
 |    12 // note. see below
 |    13
 == snap indent grid=120x41 cursor=11,12
-|2: ^  /tmp/pardes-snap/lspcomplete/cwd/a.zig * Save Tty Collapse Del TreeContext
+|2: ^* /tmp/pardes-snap/lspcomplete/cwd/a.zig * Save Tty Collapse Del TreeContext
 |12:     10     }
 == snap commentindent grid=120x41 cursor=19,14
 |14:     12 // note.     see below
@@ -28,17 +28,17 @@
 |40:      2 a.zig:3:5-12 cinnabar  cinnabar,
 == snap refill grid=120x41 cursor=16,10
 == snap step grid=120x41 cursor=19,4
-|2:    /tmp/pardes-snap/lspcomplete/cwd/a.zig * Save Tty Collapse Del TreeContext
+|2:  * /tmp/pardes-snap/lspcomplete/cwd/a.zig * Save Tty Collapse Del TreeContext
 == snap txtindent grid=120x41 cursor=15,3
 |Newcol Joincol Find Grep Help Changelog Tutor Dump NextColor Debug Exit
 |   New Tty Find Grep Joincol Delcol
-|^  /tmp/pardes-snap/lspcomplete/cwd/notes.txt * Save Tty Collapse Del
+|^* /tmp/pardes-snap/lspcomplete/cwd/notes.txt * Save Tty Collapse Del
 |     1 abc.    def ghi
 |     2
 == snap nosemi grid=100x19 cursor=29,9
 |Newcol Joincol Find Grep Help Changelog Tutor Dump NextColor Debug Exit
 |   New Tty Find Grep Joincol Delcol
-|^  /tmp/pardes-snap/lspcomplete/cwd/c.zig * Save Tty Collapse Del TreeContext
+|^* /tmp/pardes-snap/lspcomplete/cwd/c.zig * Save Tty Collapse Del TreeContext
 |     1 const Shade = enum {
 |     2     verdigris,
 |     3     cinnabar,
@@ -58,7 +58,7 @@
 == snap nobrace grid=100x19 cursor=16,10
 |Newcol Joincol Find Grep Help Changelog Tutor Dump NextColor Debug Exit
 |   New Tty Find Grep Joincol Delcol
-|^  /tmp/pardes-snap/lspcomplete/cwd/d.zig * Save Tty Collapse Del TreeContext
+|^* /tmp/pardes-snap/lspcomplete/cwd/d.zig * Save Tty Collapse Del TreeContext
 |     1 const Shade = enum {
 |     2     verdigris,
 |     3     cinnabar,