feat: add tetris shell (Tetris game TUI)

Full-screen Tetris game using Bubbletea with title screen, ghost piece,
lock delay, NES-style scoring, configurable difficulty (easy/normal/hard),
and honeypot event logging. Bumps version to 0.17.0.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

internal/shell/tetris/tetris.go

@@ -0,0 +1,66 @@
+package tetris
+
+import (
+	"context"
+	"io"
+	"time"
+
+	tea "github.com/charmbracelet/bubbletea"
+
+	"git.t-juice.club/torjus/oubliette/internal/shell"
+)
+
+const sessionTimeout = 10 * time.Minute
+
+// TetrisShell is a Tetris game TUI for the honeypot.
+type TetrisShell struct{}
+
+// NewTetrisShell returns a new TetrisShell instance.
+func NewTetrisShell() *TetrisShell {
+	return &TetrisShell{}
+}
+
+func (t *TetrisShell) Name() string        { return "tetris" }
+func (t *TetrisShell) Description() string { return "Tetris game TUI" }
+
+func (t *TetrisShell) Handle(ctx context.Context, sess *shell.SessionContext, rw io.ReadWriteCloser) error {
+	ctx, cancel := context.WithTimeout(ctx, sessionTimeout)
+	defer cancel()
+
+	difficulty := configString(sess.ShellConfig, "difficulty", "normal")
+
+	m := newModel(sess, difficulty)
+	p := tea.NewProgram(m,
+		tea.WithInput(rw),
+		tea.WithOutput(rw),
+		tea.WithAltScreen(),
+	)
+
+	done := make(chan error, 1)
+	go func() {
+		_, err := p.Run()
+		done <- err
+	}()
+
+	select {
+	case err := <-done:
+		return err
+	case <-ctx.Done():
+		p.Quit()
+		<-done
+		return nil
+	}
+}
+
+// configString reads a string from the shell config map with a default.
+func configString(cfg map[string]any, key, defaultVal string) string {
+	if cfg == nil {
+		return defaultVal
+	}
+	if v, ok := cfg[key]; ok {
+		if s, ok := v.(string); ok && s != "" {
+			return s
+		}
+	}
+	return defaultVal
+}