feat(onboard): user onboarding - no default USER.md, guided creation (#37)

- bootstrap no longer creates user/USER.md (owner direction)
- scripts/onboard.sh: name REQUIRED (interactive loop or --name),
  optional fields prompted (profession, marital, age, gender, education,
  location, timezone, skillset, interests, hobbies, pets); flag-driven
  non-interactive mode for automation
- templates/USER.md: canon skeleton, placeholder rendering, unfilled
  optional = (not provided)
- agent.sh: auto-runs onboarding when profile missing (TTY gate);
  headless run-task warns and continues without user context
- user profile dispatched to all launches (M14 layer)

Closes #37 (onboarding requirements from owner layout review)

scripts/run-task.sh

@@ -14,4 +14,8 @@ load_config
 load_release   # compose requires MOSAIC_IMAGE_TAG; task runs are release-scoped too
 bootstrap_runtime_dir
 
+if [ ! -f "$MOSAIC_DEV_DIR/user/USER.md" ]; then
+    echo "run-task: note: user profile not onboarded - continuing without user context (scripts/onboard.sh)" >&2
+fi
+
 exec node scripts/mosaic-task.mjs "$@"