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/framework/tools/health/stack-health.sh

@@ -20,7 +20,7 @@ source "$MOSAIC_HOME/tools/_lib/credentials.sh"
 FORMAT="table"
 SINGLE_SERVICE=""
 QUIET=false
-CRED_FILE="${MOSAIC_CREDENTIALS_FILE:-$HOME/src/jarvis-brain/credentials.json}"
+CRED_FILE="${MOSAIC_CREDENTIALS_FILE:-$HOME/.config/mosaic/credentials.json}"
 
 while getopts "f:s:qh" opt; do
   case $opt in