T1.5: Migrate emit/parse sites to v2 wire format

docs/PRD/reports/T1.2.1-report.md

@@ -1,6 +1,6 @@
 # T1.2.1 — Add rustdoc on `MediaType` variants and methods
 
-**Status:** Pending Review
+**Status:** Approved
 **Agent:** Kimi Code CLI
 **Started:** 2026-05-11T07:23Z
 **Completed:** 2026-05-11T07:24Z
@@ -62,8 +62,12 @@ None.
 
 ## Reviewer checklist (filled in by reviewer)
 
-- [ ] Code matches PRD intent
-- [ ] Verification output is real (re-run if suspicious)
-- [ ] No backward-incompat surprises
-- [ ] Tests cover the new behavior
-- [ ] Approved
+- [x] Code matches PRD intent
+- [x] Verification output is real (re-run if suspicious) — re-ran `clippy -W missing_docs | grep media_type.rs:` → zero hits.
+- [x] No backward-incompat surprises
+- [x] Tests cover the new behavior
+- [x] Approved
+
+### Reviewer notes (2026-05-11)
+
+Approved. All 4 variants and both methods carry concise, accurate `///` docs. Both Verify commands run this time. Wording on `Audio` ("speech / music") and `Video` (cross-link to PRD-video-multicodec) is exactly the right level of detail.