feat(m7-amend2): implicit lifecycle — writes drive state, no workflow UI

User: «Enlève également le workflow d'un test, quand on saisit des
informations côtés redteam cela signifie qu'il a été exécuté et donc
en attente d'une review blueteam.»

Backend (update_mission_test_fields)
- At the end of every PUT, inspect the touched-field set:
  - any red write on state in {pending, skipped, blocked} → state=executed
    + auto-stamp executed_at=now() if absent
  - any blue write on state=executed → state=reviewed_by_blue
- /transition endpoint kept for back-fill/admin use, not called from UI.

Frontend MissionTestPage
- Removed the transition-buttons header block and the `transition`
  mutation. State pill stays as a passive indicator.
- New labels: "Not started" / "Awaiting review" / "Reviewed" describe
  the implicit lifecycle, no longer exposing the state-machine concept.

E2E
- The SPA test that clicked `transition-executed` now verifies the
  implicit promotion: typing red fields and saving flips the pill from
  "Not started" → "Awaiting review", no button click required.

Spec
- §4 reword: "Cycle de vie implicite, piloté par les écritures" replaces
  the old "Workflow par test instance" bullet.

Tests
- 3 new pytest: red_command-alone implicit execute + auto-stamp,
  blue write promotes executed→reviewed, blue write on pending no-op.
- 142 pytest + 49 Playwright green.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

backend/app/services/mission_tests.py

@@ -591,15 +591,9 @@ def update_mission_test_fields(
 
         if "executed_at_overridden" in touched or "executed_at" in touched:
             # Editing executed_at is a red-only privilege (gated above via
-            # _RED_FIELDS). We no longer reject the write based on the
-            # current state — the spec amendement 2026-05-15 lets the red
-            # team record an execution timestamp inline, which would be
-            # circular if they had to transition the state machine first.
-            # Instead, stamping a non-null timestamp implicitly bumps the
-            # state forward from any non-executed source so the persisted
-            # record stays internally consistent. The same `mission.
-            # write_red_fields` perm covers both moves, so this isn't a
-            # privilege escalation.
+            # _RED_FIELDS). State auto-promotion is handled by the general
+            # block below; this branch just validates and applies the
+            # timestamp + override flag.
             new_overridden = (
                 bool(executed_at_overridden)
                 if "executed_at_overridden" in touched
@@ -612,11 +606,25 @@ def update_mission_test_fields(
                 )
             if "executed_at" in touched and new_at is not None and not isinstance(new_at, datetime):
                 raise InvalidTestPayload("executed_at must be an ISO datetime")
-            if new_at is not None and test.state in {"pending", "skipped", "blocked"}:
-                test.state = "executed"
             test.executed_at = new_at
             test.executed_at_overridden = new_overridden
 
+        # Implicit lifecycle (post-amendement 2026-05-15 bis): the explicit
+        # workflow is gone from the UI. A write to ANY red field implies the
+        # test was executed (auto-stamp executed_at if the operator didn't
+        # supply one); a write to ANY blue field on an executed test implies
+        # the blue team reviewed it. The /transition endpoint stays for
+        # back-fill but is no longer the primary path.
+        red_touched = bool(touched & _RED_FIELDS)
+        blue_touched = bool(touched & _BLUE_FIELDS)
+        if red_touched and test.state in {"pending", "skipped", "blocked"}:
+            if test.executed_at is None:
+                test.executed_at = datetime.now(tz=timezone.utc)
+                test.executed_at_overridden = False
+            test.state = "executed"
+        if blue_touched and test.state == "executed":
+            test.state = "reviewed_by_blue"
+
         _touch(test, viewer_id)
         s.flush()
         s.refresh(test)