Document resumable transcription and replay

docs/roadmap/implementation.md

@@ -1,6 +1,6 @@
 # Implementation Plan: Speaker Checkpoints and Replayable Uploads
 
-Status: Implementation in progress; Stages 1-6 complete.
+Status: Implementation complete; Stages 1-7 complete.
 
 ## Scope and Instructions
 
@@ -381,7 +381,19 @@ application retry/checkpoint behavior remains intact.
 
 ## Stage 7: Document and Validate the Completed Feature
 
-Status: Pending.
+Status: Complete.
+
+Completion marker (2026-09-22): Updated the canonical transcribe, merge,
+manifest, WhisperX, operations, and troubleshooting documentation for durable
+speaker reconciliation, serialized checkpoints, aggregate gating, durable
+force reset, legacy upgrade and downgrade limits, replayable streaming bodies,
+resource ownership, and the absence of an exactly-once remote guarantee.
+Reviewed the completed implementation against the feature roadmap and
+implementation-discipline guidance. Verified with `go test ./...`,
+`go test -race ./...`, `go vet ./...`, `go build ./...`,
+`go test ./internal/doccheck`,
+`go test ./internal/config -run '^TestExamplesLoadAndValidate$'`, and
+`git diff --check`.
 
 1. Update canonical transcribe and manifest internals for the collection,
    reconciliation, durable-reset force behavior, serialized saves, and aggregate