Deterministic swehockey.se schedule crawler

One HTTP GET per season, no browser: the page is server-rendered, so every row
arrives in one response and the extraction becomes a pure function of the HTML.

- layouts[] declares one profile per version of the site's table (modern and
  legacy), each identified by its header row, so a new version of the page is a
  new profile plus a fixture instead of a guess.
- The table is located by header signature, not by a CSS path.
- Every cell is shape-checked, and facts the site renders twice (desktop and
  mobile date, time in the tooltip) must agree.
- Cross-field invariants: periods sum to the score, ids are unique, played games
  always have an event link and unplayed ones never do.
- Output is sorted by date, time and id, so it does not inherit the site's row
  order, and it carries no fetch timestamp: same HTML, same bytes.
- Drift is a typed error and exit code 3, with the header it actually found.
- Tests run on committed HTML fixtures and golden JSON; TestLive is opt-in.

Verified over the full SHL archive: 27/27 seasons, 2119 games, 1779 played.

testdata/schedule_legacy_playoffs.json

@@ -0,0 +1,163 @@
+{
+  "season_id": 20961,
+  "layout": "legacy",
+  "title": "Schedule and Results",
+  "last_update": "2014-04-14 14:19",
+  "games": [
+    {
+      "game_id": "90011001",
+      "event_id": "205038",
+      "round": "1",
+      "date": "2014-03-10",
+      "time": "19:00",
+      "home": "HV 71",
+      "away": "Leksands IF",
+      "home_goals": 4,
+      "away_goals": 2,
+      "periods": [
+        {
+          "label": "1",
+          "home": 1,
+          "away": 0
+        },
+        {
+          "label": "2",
+          "home": 1,
+          "away": 1
+        },
+        {
+          "label": "3",
+          "home": 2,
+          "away": 1
+        }
+      ],
+      "spectators": 6923,
+      "venue": "Kinnarps Arena"
+    },
+    {
+      "game_id": "90011002",
+      "event_id": "205039",
+      "round": "1",
+      "date": "2014-03-10",
+      "time": "19:00",
+      "home": "Linköpings HC",
+      "away": "MODO Hockey",
+      "home_goals": 4,
+      "away_goals": 0,
+      "periods": [
+        {
+          "label": "1",
+          "home": 1,
+          "away": 0
+        },
+        {
+          "label": "2",
+          "home": 3,
+          "away": 0
+        },
+        {
+          "label": "3",
+          "home": 0,
+          "away": 0
+        }
+      ],
+      "spectators": 5853,
+      "venue": "Cloetta Center"
+    },
+    {
+      "game_id": "90011003",
+      "event_id": "205040",
+      "round": "2",
+      "date": "2014-03-12",
+      "time": "19:00",
+      "home": "Leksands IF",
+      "away": "HV 71",
+      "home_goals": 2,
+      "away_goals": 1,
+      "periods": [
+        {
+          "label": "1",
+          "home": 0,
+          "away": 1
+        },
+        {
+          "label": "2",
+          "home": 1,
+          "away": 0
+        },
+        {
+          "label": "3",
+          "home": 1,
+          "away": 0
+        }
+      ],
+      "spectators": 6018,
+      "venue": "Tegera Arena"
+    },
+    {
+      "game_id": "90011004",
+      "event_id": "205041",
+      "round": "2",
+      "date": "2014-03-12",
+      "time": "19:00",
+      "home": "MODO Hockey",
+      "away": "Linköpings HC",
+      "home_goals": 4,
+      "away_goals": 5,
+      "periods": [
+        {
+          "label": "1",
+          "home": 2,
+          "away": 0
+        },
+        {
+          "label": "2",
+          "home": 2,
+          "away": 1
+        },
+        {
+          "label": "3",
+          "home": 0,
+          "away": 3
+        },
+        {
+          "label": "4",
+          "home": 0,
+          "away": 1
+        }
+      ],
+      "spectators": 5526,
+      "venue": "Fjällräven Center"
+    },
+    {
+      "game_id": "90011005",
+      "event_id": "205042",
+      "round": "3",
+      "date": "2014-03-13",
+      "time": "19:00",
+      "home": "Leksands IF",
+      "away": "HV 71",
+      "home_goals": 2,
+      "away_goals": 4,
+      "periods": [
+        {
+          "label": "1",
+          "home": 0,
+          "away": 3
+        },
+        {
+          "label": "2",
+          "home": 0,
+          "away": 0
+        },
+        {
+          "label": "3",
+          "home": 2,
+          "away": 1
+        }
+      ],
+      "spectators": 6462,
+      "venue": "Tegera Arena"
+    }
+  ]
+}