feat(api): canon log JSON Schema + validator, enforce §7 luck boundary

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

api/tests/fixtures/canon_log_valid.json

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+{
+  "schema_version": 1,
+  "player": {
+    "name": "Aldric",
+    "class_id": "sellsword",
+    "luck_descriptor": "Fortune spits on you"
+  },
+  "location": { "id": "greywater_docks", "name": "the Greywater docks" },
+  "party": [
+    { "id": "brannoc_thane", "name": "Brannoc Thane", "disposition": 40 },
+    { "id": "cadwyn_vell", "name": "Cadwyn Vell", "disposition": 15 }
+  ],
+  "recent_events": [
+    "Arrived at Greywater by barge before dawn",
+    "Brannoc recognised the harbourmaster and went quiet"
+  ],
+  "established_facts": [
+    "the eastern bridge out of Greywater is washed out",
+    "the harbourmaster is named Oda Fenn"
+  ],
+  "active_quests": [
+    { "id": "find_the_ledger", "name": "The Missing Ledger",
+      "status": "active", "objective": "Find who took Fenn's ledger" }
+  ],
+  "humiliations": [
+    { "id": "h_0001", "text": "vomited on a shrine step in front of a priest",
+      "weight": 7, "turn": 3 }
+  ]
+}

api/tests/test_canon_log_schema.py

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+import copy
+import json
+from pathlib import Path
+
+from app.canon_log import validate_canon_log
+
+FIXTURE = Path(__file__).parent / "fixtures" / "canon_log_valid.json"
+
+
+def _valid():
+    with open(FIXTURE) as f:
+        return json.load(f)
+
+
+def test_valid_canon_log_passes():
+    assert validate_canon_log(_valid()) == []
+
+
+def test_numeric_luck_is_rejected():
+    # Charter §7: the AI must never be able to calculate Luck. A stray numeric
+    # luck field must fail validation, not slip through.
+    doc = _valid()
+    doc["player"]["luck"] = 5
+    assert validate_canon_log(doc) != []
+
+
+def test_recent_events_over_five_is_rejected():
+    doc = _valid()
+    doc["recent_events"] = [f"event {i}" for i in range(6)]
+    assert validate_canon_log(doc) != []
+
+
+def test_disposition_out_of_range_is_rejected():
+    doc = _valid()
+    doc["party"][0]["disposition"] = 200
+    assert validate_canon_log(doc) != []
+
+
+def test_unknown_quest_status_is_rejected():
+    doc = _valid()
+    doc["active_quests"][0]["status"] = "abandoned"
+    assert validate_canon_log(doc) != []
+
+
+def test_humiliation_weight_bounds_enforced():
+    doc = _valid()
+    doc["humiliations"][0]["weight"] = 11
+    assert validate_canon_log(doc) != []
+
+
+def test_empty_optional_arrays_are_allowed():
+    doc = _valid()
+    doc["party"] = []
+    doc["recent_events"] = []
+    doc["established_facts"] = []
+    doc["active_quests"] = []
+    doc["humiliations"] = []
+    assert validate_canon_log(doc) == []