Add code_review phase with approval gate, reviewer≠implementer enforcement, and structured CODE_REVIEW.md

- Insert code_review phase between implement and bug_find
- Approval gate: code_review:awaiting_approval → code_review:approved
- Read-only phase — no edits, no fixes, no returning to implement
- Reviewer≠implementer: .state.implementer tracking + --claim enforcement
- Structured CODE_REVIEW.md: spec compliance, design conformance, quality
  scorecard, items found (severity/category/location/resolution), test coverage
- Updated status.py (10 data structures), dashboard (4 files), prompts (3 files),
  agent routing, tests (6 new test classes, 19 new tests)

tests/test_framework_self_consistency.py

@@ -198,7 +198,7 @@ class TestVerdictParsingRegression:
             state, _ = determine_task_state(task_dir)
             assert state == TaskState.BLOCKED
 
-    def test_implementation_alone_is_bug_find(self):
+    def test_implementation_alone_is_implement(self):
         from automaton.dashboard.core.task import determine_task_state, TaskState
         from pathlib import Path
         import tempfile
@@ -207,7 +207,7 @@ class TestVerdictParsingRegression:
             task_dir.mkdir()
             (task_dir / "IMPLEMENTATION.md").write_text("# Implementation\nDone.\n")
             state, _ = determine_task_state(task_dir)
-            assert state == TaskState.BUG_FIND
+            assert state == TaskState.IMPLEMENT
 
     def test_empty_verdict_is_blocked(self):
         from automaton.dashboard.core.task import determine_task_state, TaskState