refactor: remove v1 multi-agent domain cluster (#599 PR1/3)

## Summary
PR 1 of 3 for #599. Removes the legacy multi-agent domain cluster and the import
"reachability threads" that kept it alive (top-level codeframe/__init__.py,
core/__init__.py, cli/__init__.py, agents/__init__.py, ui/shared.py surgery +
deleted shadowed cli.py). ~174 files, almost entirely deletions.

The plan engine (--engine plan -> BuiltinPlanAdapter -> core.agent.Agent) is
verified LIVE and intentionally KEPT.

## Validation
- Tests: pytest -m v2 green (2824 passed); Backend + Frontend CI green
- Lint/Type: ruff + mypy clean; CI Code Quality green
- Collect: pytest --collect-only clean (3863); zero tracked .py reference any deleted module
- Boot: TestClient /health -> 200; cf --help + cf status work
- Internal review: advisory (claude-review approved)
- Cross-family review: codex (3 findings fixed) + CodeRabbit (0 findings)
- Demo: all 10 acceptance criteria mapped to outcome evidence

Deferred: Database slim + enforcement/ + v1 repos (PR2); persistence->platform_store
rename + CLAUDE.md (PR3).

Part of #599 (PR1 of 3 — does not close).

Author: frankbria

codeframe/__init__.py

@@ -8,8 +8,4 @@
 __version__ = "0.1.0"
 __author__ = "Frank Bria"
 
-from codeframe.core.project import Project
-from codeframe.agents.lead_agent import LeadAgent
-from codeframe.agents.worker_agent import WorkerAgent
-
-__all__ = ["Project", "LeadAgent", "WorkerAgent"]
+__all__ = ["__version__", "__author__"]

codeframe/agents/QUICKSTART.md

@@ -1,14 +1,8 @@
-"""AI agents for CodeFRAME."""
+"""Agent utilities for CodeFRAME.
 
-from codeframe.agents.lead_agent import LeadAgent
-from codeframe.agents.worker_agent import WorkerAgent
-from codeframe.agents.factory import AgentFactory
-from codeframe.agents.definition_loader import AgentDefinitionLoader, AgentDefinition
+The legacy multi-agent orchestration (LeadAgent/WorkerAgent/AgentFactory) was
+removed during the v1 cleanup. Only the dependency resolver remains, used by the
+live ``cf`` task-scheduling commands. Import it directly:
 
-__all__ = [
-    "LeadAgent",
-    "WorkerAgent",
-    "AgentFactory",
-    "AgentDefinitionLoader",
-    "AgentDefinition",
-]
+    from codeframe.agents.dependency_resolver import ...
+"""