AgentBBS: M0 core hub, M1 arcade, pods with CoinPay membership

A modern BBS over SSH for humans and AI agents (docs/PRD.md), plus the
pods addendum (docs/pods.md). Go + charmbracelet (wish/bubbletea).

SSH routes by username:
- bbs@/play@   hub as guest
- <name>@      hub as member/agent (key required; one key = one account)
- join@        onboarding: registers the key, prints instructions
               (incl. coinpay pay command with HMAC payment ref), kicks
- pod@         personal Linux container, paid membership $1/mo via
               CoinPay; rootless podman preferred, hardened docker
               fallback (cap-drop ALL, no-new-privileges, uid 1000,
               cpu/mem/pids caps, per-user volume)

M0: plugin contract (ID/Title/Description/RequiresAuth/New + ExitMsg),
hub menu, SQLite store (users/sessions/scores/pod_subscriptions),
session audit, grant-pod ops command.

M1 arcade: doom-ascii + Freedoom via scripts/fetch-assets.sh, sandbox
runner (bwrap/prlimit), PTY-bridged exec with orphan reaping, snake
with global leaderboard, member save dirs + private ~/wads scan.

Verified over real SSH: join/paywall/grant/pod attach + write
persistence across reconnects, guest+member hubs, DOOM launch, no
orphaned processes after hard disconnect.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

plugins/arcade/ptyexec.go

@@ -0,0 +1,63 @@
+package arcade
+
+import (
+	"io"
+	"os/exec"
+
+	tea "github.com/charmbracelet/bubbletea"
+	"github.com/creack/pty"
+)
+
+// ptyExec is a tea.ExecCommand that runs the child on a real host PTY and
+// bridges it to the session streams. Needed because doom-ascii (like most
+// raw-mode terminal programs) demands an actual TTY, and over SSH the
+// bubbletea program's stdin/stdout are session streams, not a host TTY.
+type ptyExec struct {
+	cmd           *exec.Cmd
+	stdin         io.Reader
+	stdout        io.Writer
+	width, height int
+}
+
+func newPtyExec(cmd *exec.Cmd, width, height int) *ptyExec {
+	return &ptyExec{cmd: cmd, width: width, height: height}
+}
+
+func (p *ptyExec) SetStdin(r io.Reader)  { p.stdin = r }
+func (p *ptyExec) SetStdout(w io.Writer) { p.stdout = w }
+func (p *ptyExec) SetStderr(io.Writer)   {}
+
+var _ tea.ExecCommand = (*ptyExec)(nil)
+
+func (p *ptyExec) Run() error {
+	f, err := pty.StartWithSize(p.cmd, &pty.Winsize{
+		Rows: uint16(max(p.height, 24)),
+		Cols: uint16(max(p.width, 80)),
+	})
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
+	done := make(chan struct{})
+	go func() { _, _ = io.Copy(p.stdout, f); close(done) }()
+	go func() {
+		_, _ = io.Copy(f, p.stdin)
+		// Session input is gone (disconnect): don't leave the game orphaned
+		// on the host (PRD §7 S3 — abandoned sessions are reaped).
+		if p.cmd.Process != nil {
+			_ = p.cmd.Process.Kill()
+		}
+	}()
+
+	err = p.cmd.Wait()
+	<-done
+	return err
+}
+
+func max(a, b int) int {
+	if a > b {
+		return a
+	}
+	return b
+}