Checkpoint speaker transcriptions incrementally

docs/roadmap/implementation.md

@@ -1,6 +1,6 @@
 # Implementation Plan: Speaker Checkpoints and Replayable Uploads
 
-Status: Implementation in progress; Stages 1-2 complete.
+Status: Implementation in progress; Stages 1-3 complete.
 
 ## Scope and Instructions
 
@@ -186,7 +186,17 @@ work, without altering existing runtime behavior prematurely.
 
 ## Stage 3: Execute and Checkpoint Speakers Incrementally
 
-Status: Pending.
+Status: Complete.
+
+Completion marker (2026-09-21): Connected reconciliation to bounded execution,
+durably checkpointed the starting and per-speaker collections through detached
+manifest candidates, preserved committed work across failures and cancellation,
+rebuilt deterministic aggregate outputs from reusable evidence, and added
+speaker-aware resume validation. Updated production-style fixtures and covered
+serialized concurrent saves, force/retry replacement, input rechecks, save
+failures, partial recovery, and aggregate reconstruction. Verified with
+`go test ./internal/stage ./internal/app`, `go test -race ./internal/stage`, and
+`git diff --check`.
 
 Preparation: `internal/stage/transcribe.go`, `analyze_execution_state.go`,
 `run_local.go`,