fix(m6): post-review pass — cache prefix, snapshot lock, perm-before-parse, LIKE escape

Addresses spec-reviewer + code-reviewer feedback on the M6 bundle:

Critical:
- frontend/src/lib/missions.ts: add `listPrefix()` so TanStack invalidation
  catches every filtered list variant; the previous `list()` returned
  `['missions','list',{}]` and only matched the exact empty-filter cache,
  leaving filtered tables stale after create/transition/delete.
- backend/app/services/missions.py: acquire the same per-scenario
  `pg_advisory_xact_lock` key used by `set_scenario_tests` before
  snapshotting; without it a concurrent M5 reorder could freeze a torn
  snapshot under READ COMMITTED. Sorted by key to avoid deadlocks with
  another snapshotter.

Important:
- backend/app/api/missions.py: `@require_perm("mission.update",
  "mission.archive")` on the transition endpoint so users without either
  perm get 403 before the body is parsed (no shape leak via 400).
- backend/app/services/missions.py: escape `%` / `_` / `\` in user-typed
  `q` / `client` LIKE search; users can no longer trigger wildcard
  semantics by typing literal `%`. Added `escape='\\'` arg on every .like().
- backend/app/services/missions.py: filter `MissionTest.deleted_at` and
  `MissionScenario.deleted_at` in the list-item and detail counts so M7+
  soft-deletes don't drift the totals silently.

Nits:
- backend/app/api/users.py: order `/users/roster` by email for stable
  rendering + deterministic e2e selectors.
- frontend/src/pages/MissionDetailPage.tsx: distinct accent per
  transition target (cyan/orange/green/teal) matching the status legend.
- e2e/tests/m6-missions.spec.ts: switch fragile `getByRole(name=/In
  Progress/i)` to the stable `mission-transition-in_progress` data-testid.

New tests:
- test_create_mission_rejects_soft_deleted_scenario
- test_transition_perm_gate_runs_before_payload_parse
- test_search_treats_wildcards_as_literals

Suite: 106 pytest passing (was 103), 43 Playwright passing.

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

backend/app/services/missions.py

@@ -13,12 +13,13 @@ allowed (perm codes); this service enforces *which mission* is visible.
 
 from __future__ import annotations
 
+import hashlib
 import uuid
 from dataclasses import dataclass
 from datetime import date, datetime, timezone
 from typing import Any, Iterable
 
-from sqlalchemy import func, or_, select
+from sqlalchemy import func, or_, select, text
 from sqlalchemy.orm import Session, selectinload
 
 from app.db.session import session_scope
@@ -216,6 +217,40 @@ def _validate_role_hint(value: str) -> str:
     return value
 
 
+def _escape_like(raw: str) -> str:
+    """Escape LIKE wildcards so user-typed `%` / `_` / `\\` stay literal."""
+    return raw.replace("\\", "\\\\").replace("%", "\\%").replace("_", "\\_")
+
+
+def _lock_scenario_ids_for_snapshot(s: Session, scenario_ids: list[uuid.UUID]) -> None:
+    """Acquire a per-scenario `pg_advisory_xact_lock` for every source scenario
+    we're about to snapshot.
+
+    Why: a concurrent admin invoking `set_scenario_tests(scenario_id)` (M5)
+    deletes-then-reinserts the `scenario_template_tests` join rows mid-transaction.
+    Under READ COMMITTED, `_snapshot_scenarios` could observe a partial view
+    (selectinload re-queries) and freeze a torn snapshot. Sharing the same lock
+    key as `app.services.scenario_templates.set_scenario_tests` makes the
+    snapshot wait until the reorder commits (and vice versa).
+
+    The lock keys are derived deterministically from the scenario UUIDs via
+    blake2b (cf. lessons: `hash()` is randomised per-worker). We sort the keys
+    before acquiring to avoid deadlocks with another snapshotter that holds
+    them in a different order.
+    """
+    if not scenario_ids:
+        return
+    keys: list[int] = []
+    for sid in scenario_ids:
+        digest = hashlib.blake2b(sid.bytes, digest_size=8).digest()
+        keys.append(int.from_bytes(digest, "big", signed=True))
+    for key in sorted(keys):
+        s.execute(
+            text("SELECT pg_advisory_xact_lock(CAST(:key AS bigint))"),
+            {"key": key},
+        )
+
+
 def _is_member(s: Session, mission_id: uuid.UUID, viewer_id: uuid.UUID) -> bool:
     return (
         s.scalar(
@@ -390,6 +425,7 @@ def _snapshot_scenarios(
     if not scenario_ids:
         return
 
+    _lock_scenario_ids_for_snapshot(s, scenario_ids)
     sc_by_id = _load_scenario_templates_for_snapshot(s, scenario_ids)
 
     # Collect the underlying test_template ids in stable order.
@@ -495,10 +531,16 @@ def _member_views(s: Session, mission: Mission) -> list[MissionMemberView]:
 
 
 def _scenario_views(scenarios: list[MissionScenario]) -> list[MissionScenarioView]:
+    """Assemble scenario views. `mission_scenarios` and `mission_tests` both
+    carry `SoftDeleteMixin`; M6 doesn't surface soft-deletion of those rows in
+    any endpoint, but the filter is applied here so future deletions (M7+)
+    don't drift the rendered list silently."""
     views: list[MissionScenarioView] = []
-    for sc in sorted(scenarios, key=lambda s_: s_.position):
+    live = [sc for sc in scenarios if sc.deleted_at is None]
+    for sc in sorted(live, key=lambda s_: s_.position):
         test_views: list[MissionTestView] = []
-        for t in sorted(sc.tests, key=lambda t_: t_.position):
+        live_tests = [t for t in sc.tests if t.deleted_at is None]
+        for t in sorted(live_tests, key=lambda t_: t_.position):
             tag_views = [
                 MissionMitreTagView(
                     kind=tag.mitre_kind,
@@ -571,8 +613,12 @@ def _to_detail_view(s: Session, m: Mission) -> MissionView:
 
 def _to_list_item(m: Mission) -> MissionListItemView:
     # Cheap counts via the loaded relationships (selectinloaded by the caller).
+    # We filter soft-deleted children consistently with `_scenario_views` so
+    # the list and the detail page agree.
     live_scenarios = [sc for sc in m.scenarios if sc.deleted_at is None]
-    tests_count = sum(len(sc.tests) for sc in live_scenarios)
+    tests_count = sum(
+        len([t for t in sc.tests if t.deleted_at is None]) for sc in live_scenarios
+    )
     return MissionListItemView(
         id=m.id,
         name=m.name,
@@ -629,15 +675,15 @@ def list_missions(
             stmt = stmt.where(Mission.status == status)
             count_stmt = count_stmt.where(Mission.status == status)
         if client:
-            like = f"%{client.lower()}%"
-            cond = func.lower(Mission.client_target).like(like)
+            like = f"%{_escape_like(client.lower())}%"
+            cond = func.lower(Mission.client_target).like(like, escape="\\")
             stmt = stmt.where(cond)
             count_stmt = count_stmt.where(cond)
         if q:
-            like = f"%{q.lower()}%"
+            like = f"%{_escape_like(q.lower())}%"
             cond = or_(
-                func.lower(Mission.name).like(like),
-                func.lower(Mission.description_md).like(like),
+                func.lower(Mission.name).like(like, escape="\\"),
+                func.lower(Mission.description_md).like(like, escape="\\"),
             )
             stmt = stmt.where(cond)
             count_stmt = count_stmt.where(cond)