added auto-detection logic for console colour output (#817)

Add auto-detection of colour support to `AnsicolourStdoutSink`.

**New `colorMode` enum** (`On`, `Off`, `Auto`) added to the header, accepted by the `AnsicolorStdoutSink` constructor. Defaults to `Auto`, so all existing call sites are unaffected.

**`Auto` mode detection logic** (in `IscolourTerminal()`):

1. **TTY check** -- if stdout is not a terminal, colour is disabled.
2. **`NO_COLOR`** -- respects the no-colour.org convention. If set, colour is disabled.
3. **`COLORTERM`** -- if set (e.g. `truecolour`, `24bit`), colour is enabled.
4. **`TERM`** -- rejects `dumb`; accepts known colour-capable terminals via substring match:
   `alacritty`, `ansi`, `colour`, `console`, `cygwin`, `gnome`, `konsole`, `kterm`, `linux`, `msys`, `putty`, `rxvt`, `screen`, `tmux`, `vt100`, `vt102`, `xterm`.
   Substring matching covers variants like `xterm-256color` and `rxvt-unicode`.
5. **Fallback** -- Windows defaults to colour enabled (modern console supports ANSI natively); other platforms default to disabled.

When colour is disabled, ANSI escape sequences are omitted entirely from the output.

NOTE: this doesn't currently apply to all paths which do logging in zen as they may be determining their colour output mode separately from `AnsicolorStdoutSink`.

1 files changed, 8 insertions, 1 deletions

diff --git a/src/zencore/include/zencore/logging/ansicolorsink.h b/src/zencore/include/zencore/logging/ansicolorsink.h
index 9f859e8d7..5060a8393 100644
--- a/src/zencore/include/zencore/logging/ansicolorsink.h
+++ b/src/zencore/include/zencore/logging/ansicolorsink.h
@@ -8,10 +8,17 @@
 
 namespace zen::logging {
 
+enum class ColorMode
+{
+	On,
+	Off,
+	Auto
+};
+
 class AnsiColorStdoutSink : public Sink
 {
 public:
-	AnsiColorStdoutSink();
+	explicit AnsiColorStdoutSink(ColorMode Mode = ColorMode::Auto);
 	~AnsiColorStdoutSink() override;
 
 	void Log(const LogMessage& Msg) override;