chore: run live-sync heartbeat hourly

Operator decision at review: 15 min is aggressive for config churn; hourly
keeps the stale-window acceptable (<=1 h) with a fifth of the wakeups.
Timer unit, tier law, and failure-table wording aligned.

AGENTS.md

@@ -74,7 +74,7 @@ desktop GUIs. "Dirty tree" is judged by the writer:
 | Machine live | `agent/memories/`, `agent/managed-skills/`, `agent/config.yml`, `agent/models.yml` | `scripts/live-sync.sh` heartbeat |
 | Desktop live | `dotfiles/` | same heartbeat |
 
-The heartbeat (systemd user timer, ~15 min) stages ONLY allowlisted tiers,
+The heartbeat (systemd user timer, hourly) stages ONLY allowlisted tiers,
 commits with hooks armed — the secret gate included — merges `origin/main`,
 pushes, and reaps `wt/*` worktrees older than 7 days. Non-allowlist dirt is
 never committed, only surfaced. Conflicts abort and alert (ntfy); it never