[AZ-455] Step 6 close: implementation_report_tests.md + advance to Step 7

Final test-implementation report with handoff to test-run
skill per implement skill Step 16 (next flow step is Run
Tests; let test-run own the full-suite gate to avoid
duplicate runs).

27 test tasks delivered across 8 batches (1 + 4*6 + 4 + 2);
0 production source mutations; 26/26 ACs covered; 23
production drifts pinned to runnable contract tests; 29
commit-time static gates active (up from 13 at baseline).

State: existing-code Step 7 (Run Tests), not_started.

Co-authored-by: Cursor <cursoragent@cursor.com>

_docs/_autodev_state.md

@@ -2,13 +2,13 @@
 
 ## Current Step
 flow: existing-code
-step: 6
-name: Implement Tests
-status: in_progress
+step: 7
+name: Run Tests
+status: not_started
 sub_step:
-  phase: 14
-  name: batch-loop
-  detail: "Phase A closed; 25 tasks delivered; advance to Step 7"
+  phase: 0
+  name: awaiting-invocation
+  detail: ""
 retry_count: 0
 cycle: 1
 tracker: jira