feat(framework): P0 — MIT license + executable-leak sanitization

First phase of the framework constitution alpha. No behavior change for
configured installs.

- Add MIT LICENSE (root + framework bundle) + "license":"MIT" in manifests
- Drop private jarvis-brain credential fallback at 3 sites; default to
  $HOME/.config/mosaic/credentials.json (aligns with #551)
- prevent-memory-write.sh: soft-degrade OpenBrain nudge via ${OPENBRAIN_URL},
  removing hardcoded brain.woltje.com; still blocks the write

Refs #542, closes #569

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

packages/mosaic/package.json

@@ -63,5 +63,6 @@
   "files": [
     "dist",
     "framework"
-  ]
+  ],
+  "license": "MIT"
 }