revert: tea 1.0 rewrite (#1122–#1126) (#1146)

Reverts #1126, #1125, #1124, #1123 and #1122.

`go.mod` keeps the Go 1.26 line with toolchain `go1.26.9` (instead of the original `go1.26.6`) so the security fix from #1131 isn't lost.

reopens #69
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Reviewed-on: https://gitea.com/gitea/tea/pulls/1146
Reviewed-by: TheFox0x7 <95654+thefox0x7@noreply.gitea.com>

modules/theme/background.go

@@ -0,0 +1,31 @@
+// Copyright 2026 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package theme
+
+import (
+	"os"
+
+	"charm.land/lipgloss/v2"
+	"golang.org/x/term"
+)
+
+// defaultDarkBackground is the background to assume when we cannot detect one. It
+// matches the default lipgloss falls back to.
+const defaultDarkBackground = true
+
+// HasDarkBackground reports whether the terminal has a dark background.
+//
+// It only asks the terminal when stdin and stdout are both terminals. Detection
+// works by writing an escape sequence to the output and waiting for the terminal
+// to answer on the input, and nothing answers when stdio is redirected, so asking
+// means waiting on a reply that never comes. On Windows that wait is unbounded:
+// lipgloss opens the console directly rather than giving up, which is why tea used
+// to hang at start-up under a service or a CI runner.
+func HasDarkBackground() bool {
+	if !term.IsTerminal(int(os.Stdin.Fd())) || !term.IsTerminal(int(os.Stdout.Fd())) {
+		return defaultDarkBackground
+	}
+
+	return lipgloss.HasDarkBackground(os.Stdin, os.Stdout)
+}