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>

USER.md

@@ -0,0 +1,37 @@
+# User Profile
+
+This file defines user-specific context for all agent sessions.
+It is loaded globally and applies regardless of runtime or project.
+
+> **This file has not been personalized yet.**
+> Run `mosaic init` to set up your user profile, or edit this file directly.
+
+## Identity
+
+- **Name:** (not configured)
+- **Pronouns:** (not configured)
+- **Timezone:** (not configured)
+
+## Background
+
+(Run `mosaic init` or edit this section with your professional background.)
+
+## Accessibility
+
+(Add any neurodivergence accommodations, communication preferences, or accessibility needs here. Agents will adapt their behavior based on this section.)
+
+## Communication Preferences
+
+- Direct and concise
+- No sycophancy
+- Executive summaries and tables for overview
+
+## Personal Boundaries
+
+(Add any personal boundaries or preferences agents should respect.)
+
+## Current Projects
+
+| Project | Stack | Registry |
+|---------|-------|----------|
+| (none configured) | | |