hive-screen-mcp ran `grim` / `wtype` through an unbounded
`Command::output()` and spoke RFB to neatvnc with no deadline, so a
wedged compositor or a VNC server that accepts and never speaks held the
agent's turn forever. Each subprocess now has a 30s limit and is killed
when it hits it; each RFB exchange has a 10s limit. Both come back to the
agent as the tool's text result, like every other failure in this crate.
hive-c0re operator-facing text that described behaviour the code lacks:
- `hivectl matrix reset-password` printed a "next: hivectl matrix
create-user" hint that fails for every target (agents are refused, a
non-agent hits M_USER_IN_USE). The line is gone.
- a failed `nixos-container update` appended the container's journal
tail, read with `journalctl -M`. Since the job DAG, `update` only runs
from the `Swap` node on a stopped container, so the read always came
back empty. The helper is removed; the error still points at the
build log.
- the matrix sweep comment in main.rs said it re-provisions agent token
files; `ensure_all` creates no agent accounts or tokens.
- the knowledge-pull comments named a webhook caller that no longer
exists and claimed a race was "fixed at its source".
- `handle_spawn`'s doc and the `mcp_sockets` module doc named callers of
`register_agent` / a rollback that do not exist.
Refs #4723