fix(tests): merge approved procedure suggestions instead of overwriting

Approving a suggestion was replacing the template's whole procedure
field with just that submission's extracted text, silently dropping
whatever an earlier approved round had already added. Now it appends
only the genuinely new lines, so templates accumulate commands across
rounds instead of losing them.

backend/app/services/procedure_suggestion_service.py

@@ -5,7 +5,9 @@ command(s) in it are extracted heuristically (see
 ``procedure_extraction_service``) and proposed as an update to the
 originating template's suggested-procedure field. A suggestion is only
 ever created when there's a real, novel improvement to propose — nothing
-is written to the template until a lead reviews and approves it.
+is written to the template until a lead reviews and approves it, and
+approving one only ever appends new commands, never overwrites or drops
+whatever earlier approved rounds already contributed.
 """
 
 from __future__ import annotations
@@ -30,6 +32,43 @@ _TEMPLATE_FIELD = {"red": "attack_procedure", "blue": "detect_suggested_procedur
 _LEAD_ROLE = {"red": "red_lead", "blue": "blue_lead"}
 
 
+def _new_lines(current: str | None, suggested: str) -> list[str]:
+    """Lines in *suggested* not already present verbatim in *current*.
+
+    Line-level, not whole-text: a later round's extraction is usually a
+    different subset/superset of commands than an earlier one, so an exact
+    string comparison would treat almost every resubmission as "novel" and
+    then, on approval, blow away whatever an earlier approved round already
+    contributed.
+    """
+    existing = {line.strip() for line in (current or "").splitlines() if line.strip()}
+    seen: set[str] = set()
+    new: list[str] = []
+    for line in suggested.splitlines():
+        stripped = line.strip()
+        if not stripped or stripped in existing or stripped in seen:
+            continue
+        new.append(stripped)
+        seen.add(stripped)
+    return new
+
+
+def _merge_procedure_text(current: str | None, suggested: str) -> str:
+    """Append genuinely new lines from *suggested* onto *current*.
+
+    Approving a suggestion must only ever grow a template's procedure,
+    never replace it — otherwise a narrower extraction from a later round
+    would silently erase commands an earlier approved round already added.
+    """
+    current_stripped = (current or "").strip()
+    new = _new_lines(current, suggested)
+    if not new:
+        return current_stripped
+    if not current_stripped:
+        return "\n".join(new)
+    return current_stripped + "\n" + "\n".join(new)
+
+
 def create_suggestion_from_submission(db: Session, test: Test, team: str) -> ProcedureSuggestion | None:
     """Propose a template procedure improvement from *test*'s just-submitted round.
 
@@ -51,8 +90,8 @@ def create_suggestion_from_submission(db: Session, test: Test, team: str) -> Pro
     if template is None:
         return None
 
-    current = (getattr(template, _TEMPLATE_FIELD[team]) or "").strip()
-    if extracted == current:
+    current = getattr(template, _TEMPLATE_FIELD[team])
+    if not _new_lines(current, extracted):
         return None
 
     duplicate = (
@@ -116,7 +155,8 @@ def approve_suggestion(db: Session, suggestion_id: uuid.UUID, user: User) -> Pro
     if template is None:
         raise EntityNotFoundError("TestTemplate", str(suggestion.template_id))
 
-    setattr(template, _TEMPLATE_FIELD[suggestion.team], suggestion.suggested_text)
+    current_text = getattr(template, _TEMPLATE_FIELD[suggestion.team])
+    setattr(template, _TEMPLATE_FIELD[suggestion.team], _merge_procedure_text(current_text, suggestion.suggested_text))
     suggestion.status = "approved"
     suggestion.reviewed_by = user.id
     suggestion.reviewed_at = datetime.utcnow()