Add framework design docs (model-divergence, rule agents, agent tab)

Design docs in design/framework/ covering:
- Model-divergence enforcement (conflict matrix, modes, auto-assignment)
- Rule Proposer agent (daily scan, proposes rules to RULE_PROPOSALS.md)
- Rule Reviewer agent (monthly consolidation, different LLM than Proposer)
- Agent tab redesign (phase roles + scheduled jobs, remove fake types)
- Schedules, conflict-of-interest, success criteria

Cross-references updated in AGENTS.md, README.md, CHANGELOG.md,
.onboarding.md, prompts/onboarding.md, design/loops/{README,BACKLOG}.md,
memory/v1-1-hardening-session.md.

Also restores scripts/automaton-cleanup.sh stub (was corrupted by
pytest test leak writing temp path into real stub).

AGENTS.md

@@ -47,6 +47,9 @@ Automaton is a **contract-based, state-enforced workflow framework** for LLM age
 │       ├── config.py
 │       ├── core/
 │       └── ui/
+├── design/                # Design docs for major features
+│   ├── loops/             # Loop engineering system (v1 locked)
+│   └── framework/         # Framework agent features (rule agents, Agent tab, model-divergence)
 ├── tests/                 # pytest suite
 └── tasks/                 # Framework development tasks
 ```