feat: add USER.md and TOOLS.md to bootstrap framework

Introduce user profile (USER.md) and machine tool reference (TOOLS.md)
as first-class framework files. Both ship as generic defaults and are
personalized via mosaic init.

- Add USER.md/TOOLS.md defaults and parameterized templates
- Update AGENTS.md load order (6 → 8 steps)
- Update SOUL.md: default name "Assistant", add trash/mental-notes guardrails
- Update install.sh: preserve USER.md/TOOLS.md on reinstall
- Update mosaic-init: interactive USER.md + TOOLS.md generation
- Update mosaic-doctor: existence checks for new files
- Update mosaic launcher: inject USER.md/TOOLS.md into runtime prompt
- Update README: architecture diagram, generic-repo policy note

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

bin/mosaic-doctor

@@ -146,6 +146,8 @@ echo "[mosaic-doctor] Mosaic home: $MOSAIC_HOME"
 
 # Canonical Mosaic checks
 expect_file "$MOSAIC_HOME/STANDARDS.md"
+expect_file "$MOSAIC_HOME/USER.md"
+expect_file "$MOSAIC_HOME/TOOLS.md"
 expect_dir "$MOSAIC_HOME/guides"
 expect_dir "$MOSAIC_HOME/rails"
 expect_dir "$MOSAIC_HOME/rails/quality"