feat(appservice): room provisioning via bridge API (M4c, agent-comms#9)

POST /bridge/v1/provision/rooms (inside the authed bridge block): creates
rooms AS the appservice sender (PL 100 override), optional alias/topic/
invite/space. Space-link failures surface partial success (room_id +
space_linked:false + space_error) instead of orphaning the room behind an
exception (review blocker); invite list capped at 50 (review blocker:
amplification via stolen bridge token); alias length capped. 13+14 vitest.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

packages/mosaic/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@mosaicstack/mosaic",
-  "version": "0.0.31",
+  "version": "0.0.30",
   "repository": {
     "type": "git",
     "url": "https://git.mosaicstack.dev/mosaicstack/stack.git",