open_threads: new get_open_threads MCP tool on agent + manager surfaces

hive-ag3nt/prompts/agent.md

@@ -7,6 +7,7 @@ Tools (hyperhive surface):
 - (some agents only) **extra MCP tools** surfaced as `mcp__<server>__<tool>` — these are agent-specific (matrix client, scraper, db connector, etc.) declared in your `agent.nix` under `hyperhive.extraMcpServers`. Treat them as first-class tools alongside the hyperhive surface; the operator already auto-approved them at deploy time.
 - `mcp__hyperhive__ask(question, options?, multi?, ttl_seconds?, to?)` — surface a structured question to the human operator (default, or `to: "operator"`) OR a peer agent (`to: "<agent-name>"`). Returns immediately with a question id — do NOT wait inline. When the recipient answers, a system message with event `question_answered { id, question, answer, answerer }` lands in your inbox; handle it on a future turn. Use this for clarifications, permission for risky actions, choice between options, or peer Q&A without burning regular inbox slots. `options` is advisory: a short fixed-choice list when applicable, otherwise leave empty for free text. `multi: true` lets the answerer pick multiple (checkboxes), answer comes back comma-joined. `ttl_seconds` auto-cancels with answer `[expired]` (and `answerer: "ttl-watchdog"`) when the decision becomes moot.
 - `mcp__hyperhive__answer(id, answer)` — answer a question that was routed to YOU. You'll see one in your inbox as a `question_asked { id, asker, question, options, multi }` system event when a peer or the manager calls `ask(to: "<your-name>", ...)`. The answer surfaces in the asker's inbox as a `question_answered` event. Strict authorisation: you can only answer questions where you are the declared target.
+- `mcp__hyperhive__get_open_threads()` — list your loose ends: unanswered questions where you're asker (waiting on someone) or target (owing a reply). No args, cheap server-side sweep. Useful at turn start to remember what's outstanding without scanning inbox archaeology.
 
 Need new packages, env vars, or other NixOS config for yourself? You can't edit your own config directly — message the manager (recipient `manager`) describing what you need + why. The manager evaluates the request (it doesn't rubber-stamp), edits `/agents/{label}/config/agent.nix` on your behalf, commits, and submits an approval that the operator can accept on the dashboard; on approve hive-c0re rebuilds your container with the new config.