docs(milestone): complete OpenYield v0.2 (The Mesh)

---ci---
project: oy
phase: 5
milestone: v0.2
status: complete
phase_role: final
milestone_complete: true
---/ci---

Checkpoint: v0.2 milestone complete. Merged to main, tagged v0.1.5 (milestone release,
release id 732 on Gitea). All milestone branches deleted. Per run.md, checkpoint cleared
for next run (v0.3 The Bearers per ROADMAP Phase 3).

.ciagent/CHECKPOINT.json

@@ -1,11 +1,14 @@
 {
-  "phase": 4,
-  "stage": "execute",
+  "phase": 5,
+  "stage": "complete",
   "milestone": "v0.2",
   "milestone_type": "feature",
   "tag_base": "v0.1.x",
-  "phase_role": "execution",
+  "phase_role": "final",
   "project": "oy",
   "attempts": 0,
-  "updated_at": "2026-08-17T21:50:00Z"
+  "updated_at": "2026-08-17T22:00:00Z",
+  "milestone_complete": true,
+  "milestone_release_tag": "v0.1.5",
+  "release_id": 732
 }