Implement integer source units and chunk payloads

docs/integrations/seriatim.md

@@ -28,7 +28,7 @@ output that provides the same required segment fields.
   },
   "segments": [
     {
-      "id": "seg-001",
+      "id": 1,
       "start": 0,
       "end": 4,
       "speaker": "Aria",
@@ -56,10 +56,9 @@ The adapter rejects:
 - missing, null, or non-object `metadata`;
 - missing, null, non-array, or empty `segments`;
 - segment values that are not objects;
-- segment `id` values that are neither strings nor numbers;
+- segment `id` values that are not positive integer JSON numbers or numeric
+  strings;
 - non-string `speaker` or `text`;
-- empty segment IDs;
-- segment IDs with leading or trailing whitespace;
 - duplicate segment IDs;
 - missing or empty `speaker`;
 - missing, empty, invalid, non-finite, or negative `start`;
@@ -87,8 +86,7 @@ The adapter maps input to `SourceDocument`:
 
 Each segment becomes one `SourceUnit`:
 
-- `segment.id` becomes `SourceUnit.ID`; numeric IDs are converted to their JSON
-  number text, so `1` becomes `"1"`;
+- `segment.id` becomes integer `SourceUnit.ID`;
 - `segment.text` becomes `SourceUnit.Text`;
 - `SourceUnit.Kind` is `transcript_segment`;
 - `speaker`, `start`, and `end` are stored in source-unit metadata.