fix(orchestrator): run the tree timer a minute after each run

Root cause: a pkgmgr branch tree run takes 72.6 s real (55.5 s user) on
this host, while TimeoutStartSec=55 killed every run; the timer fired
again each minute, so the service burned a core and branch-tree.json
never appeared.

- kvb-orchestrator-tree.timer: OnActiveSec=30s plus
  OnUnitInactiveSec=60s instead of OnCalendar=minutely, so runs never
  overlap and the next one starts 60 s after the last ended.
- kvb-orchestrator-tree.service: TimeoutStartSec=600 and CPUQuota=50%.
- orchestrator.sh restarts the timer on install so the new schedule
  takes effect; README and requirement 001 follow.

🎯 Fix: 92 %
💥 Break: 4 %
💸 Cost: 100 %
⏱️ Time: –
🛡️ Security: 100 %
🏆 Score: 88
🚦 Gate: ✅ 90/5, cost and time <= 100, security 100 %

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/requirements/001-agent-orchestrator.md

@@ -453,8 +453,9 @@ flowchart TD
       `core.fsmonitor`).
 - [ ] `pkgmgr branch open|close|drop|gc` rewrite the file when it exists.
 - [ ] The orchestrator install enables a systemd user timer that writes it
-      every 60 s while the page polled within the last 5 min, with pkgmgr
-      built from the newest signed tag.
+      60 s after its previous run ended while the page polled within the
+      last 5 min, on at most half a core, with pkgmgr built from the newest
+      signed tag.
 - [ ] The orchestrator mounts the file read-only and reads only it.
 - [ ] `orchestrator/kvb_orchestrator/tree.py`'s git scan is gone and no
       module of the orchestrator starts `git`.