Enforce requested adapter output paths

docs/internal/stage-transcribe.md

@@ -26,6 +26,8 @@ Generate raw per-speaker transcripts from prepared audio using WhisperX.
 - prepared audio identities must be unique; prepare disambiguates distinct
   source paths that share a basename.
 - output path returned by adapter must match requested output path.
+- an empty adapter result path means the requested path; adapters cannot select
+  an alternate destination.
 - each successful output is validated before stage success, and cancellation or
   incomplete dispatch cannot be reported as a successful result.
 

docs/roadmap/implementation.md

@@ -869,6 +869,8 @@ transcripts through one artifact-owned contract.
 no output, multiple transcripts, unsafe paths, adapter conformance, and plural raw
 sources. No adapter-selected alternate path may become authoritative.
 
+**Status:** Completed.
+
 ## Stage 26 — Centralize typed extraction-bundle evidence
 
 **Read first:** `audit-findings.md` lines 3538–3568 (DUP-007) and 3907–3932