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).

design/loops/BACKLOG.md

@@ -6,6 +6,8 @@ Work queue for the self-improvement loop after task 7 lands. Items not assigned
 
 A loop configured with `work_source.kind = "backlog"` reads this file, picks the topmost `[ ]` item, drafts an implementation, transitions through phases, hands off to a human reviewer. Mark items `[x]` when complete; move items to `DONE.md` (created later) on closure.
 
+**Sibling backlog**: `design/framework/BACKLOG.md` covers framework-level agent features (rule agents, Agent tab redesign, model-divergence enforcement). A loop with `work_source.area = "framework"` reads that file instead of this one.
+
 ## v1.1 — framework manages its own docs
 
 - [ ] **design-update-loop-template** — `templates/loops/design-update/` that keeps `design/<area>/*.md` in sync with the code it documents. Triggered by `last-read-sha` drift detection.