fix(openclaw): avoid /dev/tty crash in --non-interactive and handle allowlist bootstrap

[nillin]

Summary

This patch fixes two installer failure modes seen during --upgrade on OpenClaw:

1. Headless/non-TTY installs still touched /dev/tty and failed with:
   main: line 85: /dev/tty: No such device or address
2. Config bootstrap deadlock when plugins.allow already includes claude-mem but the plugin is not installed yet.
   OpenClaw validates config before plugins install can complete, so install fails with:
   plugins.allow: plugin not found: claude-mem

Changes

• setup_tty() now short-circuits when --non-interactive is set (never opens /dev/tty).
• Added safer /dev/tty open path (-r /dev/tty + guarded exec).
• During stale-plugin cleanup before install, also remove claude-mem from plugins.allow temporarily.
• Restore plugins.allow entry after successful install+enable if it existed previously.

Why this is safe

• Allowlist handling is round-trip: only restored when it existed originally.
• Existing plugin config restoration logic (entries.claude-mem.config) remains intact.
• Interactive behavior is unchanged for normal TTY sessions.

Validation

• bash -n openclaw/install.sh passes.
• Reproduced both failures on a live OpenClaw host, applied this logic, and confirmed upgrade completes and memory plugin loads.