chore: planning gate — milestones, issues, and task breakdown

Break PRD into 8 milestones (Phase 0–7) with 59 issues on Gitea.
Populate TASKS.md, update mission manifest, initialize scratchpad.
Repo created at git.mosaicstack.dev/mosaic/mosaic-stack.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.mosaic/orchestrator/next-task.json

@@ -0,0 +1,19 @@
+{
+  "generated_at": "2026-03-13T00:44:51Z",
+  "runtime": "claude",
+  "mission_id": "mvp-20260312",
+  "mission_name": "MVP",
+  "project_path": "/home/jwoltje/src/mosaic-mono-v1",
+  "quality_gates": "",
+  "current_milestone": {
+    "id": "",
+    "name": ""
+  },
+  "next_task": "",
+  "progress": {
+    "tasks_done": 0,
+    "tasks_total": 0,
+    "pct": 0
+  },
+  "current_branch": ""
+}