feat(comms): P1 presence — minimal Synapse + fleet presence room + mosaic.presence heartbeat + liveness (#888)

Co-authored-by: jason.woltje <jason@diversecanvas.com>
Co-committed-by: jason.woltje <jason@diversecanvas.com>

tools/matrix-presence-harness/package.json

@@ -0,0 +1,24 @@
+{
+  "name": "@mosaicstack/matrix-presence-harness",
+  "version": "0.0.1",
+  "type": "module",
+  "private": true,
+  "description": "DEV-ONLY validation harness for RFC-001 P1 (Matrix presence). Not shipped.",
+  "scripts": {
+    "build": "tsc --noEmit",
+    "lint": "eslint .",
+    "typecheck": "tsc --noEmit",
+    "test": "vitest run --passWithNoTests",
+    "validate": "./run.sh"
+  },
+  "dependencies": {
+    "@mosaicstack/appservice": "workspace:*",
+    "@mosaicstack/comms": "workspace:*"
+  },
+  "devDependencies": {
+    "@types/node": "^22.0.0",
+    "tsx": "^4.19.0",
+    "typescript": "^5.8.0",
+    "vitest": "^2.0.0"
+  }
+}