Let herdr's tab bar show the terminal background, so it turns glassy too (#15022)

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

test/shell.d/herdr-glassy-tab-bar-migration-test.sh

@@ -0,0 +1,50 @@
+#!/bin/bash
+
+set -euo pipefail
+
+source "$(dirname "$0")/base-test.sh"
+
+migration="$ROOT/migrations/1791722809.sh"
+test_dir=$(mktemp -d)
+trap 'rm -rf "$test_dir"' EXIT
+
+config="$test_dir/.config/herdr/config.toml"
+mkdir -p "${config%/*}" "$test_dir/bin"
+
+# Reloading herdr would reach the developer's own server.
+printf '#!/bin/bash\necho restart >>"$TEST_LOG"\n' >"$test_dir/bin/omarchy-restart-herdr"
+chmod +x "$test_dir/bin/omarchy-restart-herdr"
+
+run_migration() {
+  : >"$test_dir/log"
+  HOME="$test_dir" PATH="$test_dir/bin:$PATH" TEST_LOG="$test_dir/log" bash -euo pipefail "$migration" >/dev/null
+}
+
+cp "$ROOT/config/herdr/config.toml" "$test_dir/shipped.toml"
+sed -i '/^# The tab bar sits/,/^surface_dim = "black"$/c\# The active tab is drawn as panel_bg text on an accent background\npanel_bg = "black"' "$test_dir/shipped.toml"
+cp "$test_dir/shipped.toml" "$config"
+
+run_migration
+grep -qx 'panel_bg = "reset"' "$config" && (( $(grep -c '^surface_dim' "$config") == 1 )) ||
+  fail "the shipped black tab bar takes the terminal background" "$(cat "$config")"
+grep -qx restart "$test_dir/log" || fail "herdr reloads after the change"
+run_migration
+[[ ! -s $test_dir/log ]] || fail "a second run changes nothing"
+pass "the shipped black tab bar takes the terminal background, once"
+
+# A surface_dim of the user's own, indented or not, is kept as the only one.
+{ cat "$test_dir/shipped.toml"; printf '  surface_dim = "white"\n'; } >"$config"
+cp "$config" "$test_dir/custom.toml"
+run_migration
+cmp -s "$config" "$test_dir/custom.toml" || fail "an indented surface_dim of the user's own is kept, with no second one"
+pass "a surface_dim of the user's own is kept, with no second one"
+
+# A config a dotfile manager links in is left for it to manage.
+mkdir -p "$test_dir/dotfiles"
+cp "$test_dir/shipped.toml" "$test_dir/dotfiles/config.toml"
+rm "$config"
+ln -s "$test_dir/dotfiles/config.toml" "$config"
+run_migration
+[[ -L $config ]] && cmp -s "$test_dir/dotfiles/config.toml" "$test_dir/shipped.toml" ||
+  fail "a linked herdr config is left linked and unchanged"
+pass "a linked herdr config is left alone"