feat(pty): add server ownership and restart handoff - #6

Summary

• Make ownership mandatory for every daemon. Plain opencode-pty daemon requires one authenticated owner connection; there is no unmanaged mode or opt-in flag.
• Stop the daemon and its terminals when the owner disconnects, except during an explicit bounded restart handoff.
• Preserve terminal processes through single-use handoff tickets, with a fixed 120-second deadline and 5-second initial acquisition window.
• Make the playground own its daemon and shut it down on exit. Observer commands only connect to existing daemons.
• Use protocol 7, including the latest terminal-row operations. Remove stale database-keyed discovery documentation; the companion OpenCode integration uses per-server UUID directories.

Verification

• cargo test: 32 tests passed
• cargo fmt --check
• cargo clippy --all-targets --all-features -- -D warnings
• OpenCode transport/server integration tests passed against the local daemon
• Real-process checks passed for graceful exit, killing the standalone CLI, and killing its server: server, daemon, and terminal all exited

Release Notes

Based on current master, including the published 0.1.12 changes. No new package version or release tag is included, and no package has been published for this PR.