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>

tests/Minesweeper.Core.Tests/Minesweeper.Core.Tests.csproj

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