Added support for a minimal JSON output schema

architecture.md

@@ -216,6 +216,7 @@ seriatim merge \
   --preprocessing-modules validate-raw,normalize-speakers,trim-text \
   --postprocessing-modules detect-overlaps,resolve-overlaps,backchannel,filler,coalesce,detect-overlaps,autocorrect,assign-ids,validate-output \
   --output-modules json \
+  --output-schema seriatim \
   --output-file merged.json \
   --report-file report.json
 ```
@@ -260,7 +261,7 @@ type Postprocessor interface {
 
 type OutputWriter interface {
 	Name() string
-	Write(ctx context.Context, out FinalTranscript, report Report, cfg Config) ([]ReportEvent, error)
+	Write(ctx context.Context, out any, report Report, cfg Config) ([]ReportEvent, error)
 }
 ```
 
@@ -386,7 +387,7 @@ A valid merged transcript should satisfy:
 - Any `overlap_group_id` on a segment refers to an existing overlap group.
 - Every overlap group references at least two segments.
 - Every referenced segment exists.
-- Output validates against the output schema.
+- Output validates against the selected output schema.
 
 ## Determinism Requirements