Render theme templates in one awk pass (#13406)

A theme switch waits on omarchy-theme-set-templates before the shell
transition starts, and it spent ~670ms spawning processes: a subshell
per color for its rgb form, a grep per template per function family, an
awk per mix, and a sed per template matching every line against
hundreds of patterns.

Helpers now return through REPLY, one grep finds the function tokens
across all templates, and one awk computes the mixes with the same
floating point rounding and renders every template. Output is byte for
byte identical across all shipped themes. Generation takes ~65ms, and
the transition starts ~130ms after omarchy-theme-set begins instead of
~740ms.

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

test/shell.d/theme-templates-test.sh

@@ -0,0 +1,78 @@
+#!/bin/bash
+
+set -euo pipefail
+
+source "$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")" && pwd)/base-test.sh"
+
+test_tmp=$(mktemp -d)
+trap 'rm -rf "$test_tmp"' EXIT
+
+home="$test_tmp/home"
+next="$home/.local/state/omarchy/current/next-theme"
+themed="$home/.config/omarchy/themed"
+mkdir -p "$next" "$themed"
+
+cat >"$next/colors.toml" <<'EOF'
+accent = "#ff0000"
+foreground = "#e0e0e0"
+background = "#000000"
+red = "#ff0000"
+blue = "#0000ff"
+hyprland_active_border = "0xffa8b0c0 rgb(10,20,300,0.5) accent -12.5deg"
+EOF
+
+cat >"$themed/probe.txt.tpl" <<'EOF'
+plain={{ accent }} {{ accent_strip }} {{ accent_rgb }}
+round={{ mix background accent 30% }} {{ mix background accent 0.3 }} {{ mix background accent 12.5% }} {{ mix background accent 150 }}
+variants={{ mix_strip background accent 30% }} {{ mix_rgb red blue 50% }}
+spacing={{  mix   background   accent   30%  }} {{accent}}
+untouched={{ mix nope accent 30% }} {{ mix background accent }} {{ unknown_key }} {{{ accent }}}
+hypr={{ hypr_gradient hyprland_active_border accent }} {{ hypr_gradient missing_border rgba(00000000) }} {{ hypr_gradient missing_border }}
+start={{ gradient_start hyprland_active_border accent }} {{ gradient_start missing_border 0xff112233 }}
+shell={{ shell_gradient hyprland_active_border accent }}
+EOF
+
+# A user template shadows the built-in of the same name, a file the theme ships
+# is never overwritten, and an empty template still leaves its file behind.
+printf 'user {{ accent }}\n' >"$themed/kitty.conf.tpl"
+printf 'shipped\n' >"$next/foot.ini"
+: >"$themed/empty.txt.tpl"
+printf 'no newline {{ accent }}' >"$themed/tail.txt.tpl"
+# Function arguments may be separated by any whitespace, tabs included.
+printf '{{ mix\tbackground accent 30%% }} {{\tmix_rgb red\tblue 50%%\t}} {{ gradient_start\thyprland_active_border accent }}\n' >"$themed/tabs.txt.tpl"
+
+HOME="$home" OMARCHY_PATH="$ROOT" PATH="$ROOT/bin:$PATH" "$ROOT/bin/omarchy-theme-set-templates"
+
+# Expected values were produced by the sed-based renderer this replaced, so
+# every theme keeps rendering byte for byte the same.
+expected=$(cat <<'EOF'
+plain=#ff0000 ff0000 255,0,0
+round=#4d0000 #4d0000 #200000 #ff0000
+variants=4d0000 128,0,128
+spacing=#4d0000 {{accent}}
+untouched={{ mix nope accent 30% }} {{ mix background accent }} {{ unknown_key }} {#ff0000}
+hypr={ colors = { "0xffa8b0c0", "rgb(10,20,300,0.5)", "#ff0000" }, angle = -12.5 } "rgba(00000000)" "missing_border"
+start=#a8b0c0 #112233
+shell=0xffa8b0c0 rgb(10,20,300,0.5) #ff0000 -12.5deg
+EOF
+)
+
+[[ $(<"$next/probe.txt") == "$expected" ]] ||
+  fail "theme templates render values, mixes and gradients as before: $(diff <(printf '%s\n' "$expected") "$next/probe.txt")"
+pass "theme templates render values, mixes and gradients as before"
+
+[[ $(<"$next/tabs.txt") == "#4d0000 128,0,128 #a8b0c0" ]] || fail "theme templates resolve function tokens separated by tabs"
+pass "theme templates resolve function tokens separated by tabs"
+
+[[ $(<"$next/kitty.conf") == "user #ff0000" ]] || fail "a user template shadows the built-in of the same name"
+[[ $(<"$next/foot.ini") == "shipped" ]] || fail "a file the theme ships is not overwritten"
+[[ -f $next/empty.txt && ! -s $next/empty.txt ]] || fail "an empty template still produces its file"
+[[ $(od -An -c "$next/tail.txt" | tr -d ' \n') == *"#ff0000" ]] || fail "a template without a final newline renders without one"
+pass "theme templates keep user, theme and file-ending precedence"
+
+for tpl in "$ROOT"/default/themed/*.tpl; do
+  name=${tpl##*/}
+  name=${name%.tpl}
+  [[ -f $next/$name ]] || fail "every built-in template renders ($name)"
+done
+pass "theme templates render every built-in template"