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/config.json

@@ -0,0 +1,22 @@
+{
+  "enabled": false,
+  "transport": "matrix",
+  "matrix": {
+    "control_room_id": "",
+    "workspace_id": "",
+    "homeserver_url": "",
+    "access_token": "",
+    "bot_user_id": ""
+  },
+  "worker": {
+    "runtime": "codex",
+    "command_template": "bash scripts/agent/orchestrator-worker.sh {task_file}",
+    "timeout_seconds": 7200,
+    "max_attempts": 1
+  },
+  "quality_gates": [
+    "pnpm lint",
+    "pnpm typecheck",
+    "pnpm test"
+  ]
+}