Use recovery and time explainers in three challenges

challenges/journal-recovery-easy/statement.json

@@ -8,17 +8,10 @@
     {
       "kind": "figure",
       "label": "FIG 1",
+      "presentation": "immersive",
       "illustration": {
-        "id": "systems.frames",
-        "props": {
-          "title": "The durable prefix ends after LSN 2",
-          "note": "recovery scans left to right",
-          "frames": [
-            { "label": "LSN 1", "status": "synced", "tone": "signal", "fields": [{ "label": "magic", "tone": "accent" }, { "label": "len + seq", "tone": "accent" }, { "label": "payload", "tone": "signal" }, { "label": "CRC", "tone": "warning" }] },
-            { "label": "LSN 2", "status": "synced", "tone": "signal", "fields": [{ "label": "magic", "tone": "accent" }, { "label": "len + seq", "tone": "accent" }, { "label": "payload", "tone": "signal" }, { "label": "CRC", "tone": "warning" }] },
-            { "label": "LSN 3", "status": "torn tail", "tone": "danger", "fields": [{ "label": "magic", "tone": "accent" }, { "label": "len + seq", "tone": "accent" }, { "label": "partial", "detail": "payload", "tone": "danger" }, { "label": "missing", "detail": "bytes + CRC", "tone": "neutral" }], "note": "A declared frame that ends early is not applied." }
-          ]
-        }
+        "id": "systems.journal-story",
+        "props": {}
       },
       "caption": "Append gives a record an LSN, but only Sync makes the requested prefix durable. Recovery trusts structure and checksum, not intent."
     },

challenges/lsm-compactor-easy/statement.json

@@ -8,20 +8,10 @@
     {
       "kind": "figure",
       "label": "FIG 1",
+      "presentation": "immersive",
       "illustration": {
-        "id": "systems.ranges",
-        "props": {
-          "title": "Selecting A + B closes over both Level-1 runs",
-          "min": 0,
-          "max": 60,
-          "rows": [
-            { "label": "L0 A", "start": 10, "end": 30, "tone": "warning", "note": "Selected run" },
-            { "label": "L0 B", "start": 25, "end": 50, "tone": "warning", "note": "Selected run, overlaps A" },
-            { "label": "L1 X", "start": 0, "end": 20, "tone": "accent", "note": "Must join: overlaps A" },
-            { "label": "L1 Y", "start": 40, "end": 60, "tone": "accent", "note": "Must join: overlaps B" }
-          ],
-          "markers": [{ "at": 10, "label": "union starts", "tone": "signal" }, { "at": 50, "label": "union ends", "tone": "signal" }]
-        }
+        "id": "systems.lsm-story",
+        "props": {}
       },
       "caption": "The selected Level-0 range spans keys 10 to 50. Both Level-1 runs intersect it, so a legal merge must include X and Y."
     },

challenges/stream-windows-easy/statement.json

@@ -8,20 +8,12 @@
     {
       "kind": "figure",
       "label": "FIG 1",
+      "presentation": "immersive",
       "illustration": {
-        "id": "systems.ranges",
-        "props": {
-          "title": "Half-open windows on the event-time axis",
-          "min": 0,
-          "max": 20,
-          "rows": [
-            { "label": "[0, 10)", "start": 0, "end": 10, "tone": "signal", "note": "api +3 and api +5 · emit count 2, sum 8" },
-            { "label": "[10, 20)", "start": 10, "end": 20, "tone": "warning", "note": "db +2 · still live at watermark 10" }
-          ],
-          "markers": [{ "at": 10, "label": "watermark", "tone": "accent" }]
-        }
+        "id": "systems.window-story",
+        "props": {}
       },
-      "caption": "At watermark 10, Window 0 is final: emit api(count=2, sum=8) and evict it. Window 1 remains live."
+      "caption": "Tick 9 belongs to [0,10); tick 10 begins [10,20). Watermark 10 emits the first aggregate once and evicts it while the second window stays live."
     },
     {
       "kind": "callout",