chore(config): add workflow block — 4 standing rules

Adds a top-level workflow block to .ciagent/config.json with the four
standing rules for v0.2+ and all future milestones:

1. no_hitl: true              — full automation, no human-in-the-loop
2. merge_strategy             — fast-forward or rebase-then-fast-forward only;
                                  no merge-commit-no-ff, no squash
3. release_flow_per_phase: true — every phase tag produces a Gitea release
                                  (already in .ciagent/RELEASE_POLICY.md, now
                                  also enforced in config.json)
4. branching                  — main < milestone/<slug> < phase/<NN>-<slug>
                                  phase branches FF into milestone;
                                  milestone rebases onto main then FF.

---ci---
project: orca
phase: 0
milestone: v0.1
status: execute
---/ci---

.ciagent/config.json

@@ -31,6 +31,22 @@
     "max_verification_retries": 2,
     "escalation_hooks": ["delete", "drop", "force", "reset --hard"]
   },
+  "workflow": {
+    "no_hitl": true,
+    "release_flow_per_phase": true,
+    "merge_strategy": {
+      "allowed": ["fast-forward", "rebase-then-fast-forward"],
+      "forbidden": ["merge-commit-no-ff", "squash"],
+      "phase_to_milestone": "fast-forward",
+      "milestone_to_main": "rebase-then-fast-forward"
+    },
+    "branching": {
+      "hierarchy": "main < milestone/<slug> < phase/<NN>-<slug>",
+      "phase_branches": "phase/NN-<slug> merges into milestone/<slug> via fast-forward",
+      "milestone_branches": "milestone/<slug> rebases onto main, then fast-forwards main",
+      "default_branch": "main"
+    }
+  },
   "personas": {
     "enabled": true,
     "territory_enforcement": "warn",