feat(box): passkey fetch, agent key-approval flow, unified lookups, tmux agent UX

- box passkey [show|fetch] (+ muse passkey): documents VM-only passkey
  (/srv/box/passkey.txt, fallback /etc/netvm/passkey.txt on 34.139.37.135),
  probes VM over SSH with graceful fallback; --json supported. No secrets on bl.
- approvals: request_key_approval / check_node_key_request; KEY_APPROVAL status
  surfaced in `box approvals check`; allow/deny resolve + audit to box-ctl.jsonl;
  never auto-approved. New `box approvals request-key <node> --reason`.
- box lookup (summary|fleet|threads|unread|approvals|key|docs) and docs-lookup
  engine with lookup_internal/ database (docs_internal symlink).
- muse-tmux: non-TTY attach falls back to scrollback capture; prune NameError fix.
- box/muse passthrough for tmux/muse/docs; thread list/view alias + prefix resolve.
- Docs: AGENTS.md, AGENT-TOOLING.md, BOX-WEB-SURFACE-GUIDE.md, README.
- Tests: key-approval + passkey tests; sync stale sidechat UUIDs and manifest name.
- .gitignore runtime trackers (subagent-sessions, conversation-nudge-tracker).

bin/self_main_loop.py

@@ -280,10 +280,17 @@ def make_digest_id(agent):
 # recursive box->agent->box discipline: post the RESULT back in this thread
 # (box records it and dispatches the next chained step); never DM the next
 # agent directly. ~166 chars, within the 600-char digest budget.
-CONTRACT_FOOTER = ("Reply: [ACK id] seen | [CLAIM id] mine | "
-                   "[RESULT id] done | [DECLINE id] | [NO-ACTION id]. "
-                   "Report back here. Box dispatches the next step; "
-                   "do not DM the next agent directly.")
+try:
+    import lookup_engine
+    HAS_LOOKUP_ENGINE = True
+except ImportError:
+    HAS_LOOKUP_ENGINE = False
+
+_DEFAULT_CONTRACT_FOOTER = ("Reply: [ACK id] seen | [CLAIM id] mine | "
+                           "[RESULT id] done | [DECLINE id] | [NO-ACTION id]. "
+                           "Report back here. Box dispatches the next step; "
+                           "do not DM the next agent directly.")
+CONTRACT_FOOTER = lookup_engine.get_contract_footer() if HAS_LOOKUP_ENGINE else _DEFAULT_CONTRACT_FOOTER
 
 
 def send_prompt(sender, agent, sidechat, digest):