T6.3: Design exploration for federated reputation gossip

Add docs/PRD/PRD-relay-federation-gossip.md comparing 3 approaches:
1. Push gossip — relay broadcasts RepeatAbusive verdicts to peers
2. Pull oracle — peers query a reputation oracle periodically
3. Ban-list distribution — admin signs and pushes authoritative list

For each: wire format, Sybil resistance, convergence, storage,
partition tolerance, failure modes. Open questions block implementation
(trust model, privacy leakage, key infrastructure). Move T6.3 to Blocked
pending reviewer design call.

docs/PRD/reports/T6.1-report.md

@@ -110,7 +110,6 @@ $ cargo clippy -p wzp-video --all-targets -- -D warnings
 1. **Full I420 decode in dav1d** — Currently copies only Y plane. U/V plane handling can be added when the renderer needs it; the `VideoFrame` API already supports arbitrary `data` layout.
 2. **Android device validation (T6.1.1)** — Same deferred status as T4.3.1.1. Needs physical Android 10+ device with AV1 HW support.
 3. **AV1 output format assumption** — `MediaCodecAv1Encoder` assumes Android outputs raw OBU data directly. If future Android versions change the output container format, `drain_output()` may need a conversion helper analogous to `avcc_to_annexb`.
-4. **Full I420 decode in dav1d** — Currently copies only Y plane. U/V plane handling can be added when the renderer needs it; the `VideoFrame` API already supports arbitrary `data` layout.
 
 ## Reviewer checklist (filled in by reviewer)
 

docs/PRD/reports/T6.1.2-report.md

@@ -4,7 +4,7 @@
 **Agent:** Kimi Code CLI
 **Started:** 2026-05-12T18:50Z
 **Completed:** 2026-05-12T19:15Z
-**Commit:** d904763
+**Commit:** 086d0a4
 **PRD:** ../PRD-video-multicodec.md
 
 ## What I changed