Allow checkpoints for empty audio accepted by WhisperX

docs/roadmap/remediation.md

@@ -1,6 +1,6 @@
 # Transcription Checkpoint Review Remediation
 
-Status: Open.
+Status: Complete.
 
 Reviewed commits `7b0bf99` through `96b4e73` against the speaker-checkpoint and
 upload-replay roadmap and the original user request. No production changes were
@@ -56,7 +56,13 @@ correct rebuilt outputs, and no removed speaker reaching merge.
 
 ## 2. Remove the Unrequested Positive Audio-Size Requirement
 
-Priority: P2. Status: Pending.
+Priority: P2. Status: Complete.
+
+Audio evidence now permits zero size while still rejecting negative values.
+Regression tests verify zero-size manifest round trips, successful service
+results being checkpointed and reused, and service rejection being propagated
+without creating a completion record. Nonempty valid-JSON output validation is
+unchanged. Both new success regressions failed before the fix.
 
 Location: `internal/manifest/transcribe_state.go:95`.
 
@@ -90,7 +96,9 @@ ordinary downstream-failure tests.
 
 ## Verification After Remediation
 
-Run focused stage/manifest/application tests, changed-package race tests, and
-the standard repository validation gates from `docs/development.md`. Preserve
-the existing replay and cancellation regression tests; these findings do not
-require redesigning the HTTP adapter.
+Completed on 2026-09-22 with Go 1.26.8: focused stage/application tests,
+changed-package race tests, `go test ./...`, `go test -race ./...`,
+`go vet ./...`, `go build ./...`, `go test ./internal/doccheck`,
+`go test ./internal/config -run '^TestExamplesLoadAndValidate$'`, and
+`git diff --check` all passed. Existing replay and cancellation regression
+tests remain intact; the HTTP adapter required no changes.