Add console Minesweeper with a UI-free engine

Rules and board state live in Minesweeper.Core with no console calls, so the same board drives both the CLI and the tests.

Engine: seeded or random boards with classic presets; first click always safe (and its ring too when the board has room); cascading reveal that stops at numbers; flagging and chording; win by clearing every safe cell; FromMines() for deterministic layouts.

CLI: typed commands ("3 4", "f 2 5", "chord 6 7") plus optional arrow-key mode. Rows numbered, columns lettered, player input 1-based while engine coordinates stay 0-based, with CommandParser the only place that converts. ANSI colour when writing to a terminal, plain when redirected or NO_COLOR is set.

Tests: 186 covering flood-fill bounds, first-click safety, chording, win/loss, command parsing, session behaviour, and renderer alignment with colour on and off.

Co-authored-by: openhands <openhands@all-hands.dev>

src/Minesweeper.Cli/CommandParser.cs

@@ -0,0 +1,94 @@
+using System.Globalization;
+using Minesweeper.Core;
+
+namespace Minesweeper.Cli;
+
+/// <summary>Turns typed text and raw keystrokes into <see cref="Command"/> instances. This is the
+/// only place that translates the one-based coordinates a player sees into engine coordinates.</summary>
+public static class CommandParser
+{
+    /// <summary>Parses a typed line. Coordinates are one-based, e.g. <c>reveal 3 4</c>.</summary>
+    public static Command Parse(string input)
+    {
+        var text = input.Trim();
+        if (text.Length == 0)
+        {
+            return new Command.Noop();
+        }
+
+        var parts = text.Split([' ', ',', ';', '\t'], StringSplitOptions.RemoveEmptyEntries);
+        var verb = parts[0].ToLowerInvariant();
+
+        switch (verb)
+        {
+            case "q" or "quit" or "exit":
+                return new Command.Quit();
+            case "n" or "new":
+                return new Command.NewGame();
+            case "h" or "help" or "?":
+                return new Command.ShowHelp();
+            case "d" or "difficulty":
+                return ParseDifficulty(parts, text);
+            case "r" or "reveal" or "open":
+                return ParseCell(parts, 1, cell => new Command.Reveal(cell), text);
+            case "f" or "flag" or "mark":
+                return ParseCell(parts, 1, cell => new Command.Flag(cell), text);
+            case "c" or "chord":
+                return ParseCell(parts, 1, cell => new Command.Chord(cell), text);
+            case "go" or "goto":
+                return ParseCell(parts, 1, cell => new Command.SetCursor(cell), text);
+        }
+
+        // A bare "3 4" reveals that cell, since revealing is by far the most common action.
+        return ParseCell(parts, 0, cell => new Command.Reveal(cell), text);
+    }
+
+    /// <summary>Maps a keystroke from keyboard-driven mode onto a command.</summary>
+    public static Command FromKey(ConsoleKeyInfo key) => key.Key switch
+    {
+        ConsoleKey.UpArrow => new Command.MoveCursor(-1, 0),
+        ConsoleKey.DownArrow => new Command.MoveCursor(1, 0),
+        ConsoleKey.LeftArrow => new Command.MoveCursor(0, -1),
+        ConsoleKey.RightArrow => new Command.MoveCursor(0, 1),
+        ConsoleKey.Enter or ConsoleKey.Spacebar => new Command.RevealAtCursor(),
+        ConsoleKey.F => new Command.FlagAtCursor(),
+        ConsoleKey.C => new Command.ChordAtCursor(),
+        ConsoleKey.N => new Command.NewGame(),
+        ConsoleKey.D1 => new Command.ChangeDifficulty(GameDifficulty.Beginner),
+        ConsoleKey.D2 => new Command.ChangeDifficulty(GameDifficulty.Intermediate),
+        ConsoleKey.D3 => new Command.ChangeDifficulty(GameDifficulty.Expert),
+        ConsoleKey.Escape or ConsoleKey.Q => new Command.Quit(),
+        _ => new Command.Noop(),
+    };
+
+    private static Command ParseDifficulty(string[] parts, string text)
+    {
+        if (parts.Length < 2)
+        {
+            return new Command.ShowHelp();
+        }
+
+        return parts[1].ToLowerInvariant() switch
+        {
+            "1" or "b" or "beginner" or "easy" => new Command.ChangeDifficulty(GameDifficulty.Beginner),
+            "2" or "i" or "intermediate" or "medium" => new Command.ChangeDifficulty(GameDifficulty.Intermediate),
+            "3" or "e" or "expert" or "hard" => new Command.ChangeDifficulty(GameDifficulty.Expert),
+            _ => new Command.Unknown(text),
+        };
+    }
+
+    private static Command ParseCell(string[] parts, int offset, Func<CellLocation, Command> factory, string text)
+    {
+        if (parts.Length - offset < 2 ||
+            !TryParseCoordinate(parts[offset], out var row) ||
+            !TryParseCoordinate(parts[offset + 1], out var column))
+        {
+            return new Command.Unknown(text);
+        }
+
+        return factory(new CellLocation(row - 1, column - 1));
+    }
+
+    private static bool TryParseCoordinate(string token, out int value) =>
+        int.TryParse(token, NumberStyles.None, CultureInfo.InvariantCulture, out value) && value > 0;
+}