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/_lib/credentials.sh

@@ -17,10 +17,10 @@
 # Run `load_credentials --help` for details.
 
 if [[ -z "${MOSAIC_CREDENTIALS_FILE:-}" ]]; then
-  for _cand in "$HOME/.config/mosaic/credentials.json" "$HOME/src/jarvis-brain/credentials.json"; do
+  for _cand in "$HOME/.config/mosaic/credentials.json"; do
     if [[ -f "$_cand" ]]; then MOSAIC_CREDENTIALS_FILE="$_cand"; break; fi
   done
-  : "${MOSAIC_CREDENTIALS_FILE:=$HOME/src/jarvis-brain/credentials.json}"
+  : "${MOSAIC_CREDENTIALS_FILE:=$HOME/.config/mosaic/credentials.json}"
 fi
 
 _mosaic_require_jq() {