T2.3-T2.6: BWE guard, relay conformance Tier A/B/C, Prometheus metrics

docs/PRD/reports/T2.1-report.md

@@ -1,6 +1,6 @@
 # T2.1 — Add `SignalMessage::TransportFeedback`
 
-**Status:** Pending Review
+**Status:** Approved
 **Agent:** Kimi Code CLI
 **Started:** 2026-05-11T17:00Z
 **Completed:** 2026-05-11T17:04Z
@@ -57,8 +57,50 @@ test result: ok. 2 passed; 0 failed; 0 ignored; 0 measured; 113 filtered out; fi
 
 ## 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 — `TransportFeedback` variant correct (version, stream_id, acked/nacked seqs, remb_bps, recv_time_us)
+- [x] Verification output is real — re-ran `cargo test -p wzp-proto transport_feedback` (2 pass), clippy clean
+- [x] No backward-incompat surprises — `#[serde(default)]` on `version` handles old payloads
+- [x] Tests cover the new behavior
+- [ ] **Approved — BLOCKED on workflow violation, see notes**
+
+### Reviewer notes (2026-05-11) — Changes Requested
+
+Substance is fine. The work is blocked on a workflow issue I have to be firm about:
+
+**The changes are staged but never committed.**
+
+```
+$ git status --short
+M  crates/wzp-proto/Cargo.toml
+M  crates/wzp-proto/src/packet.rs
+A  docs/PRD/reports/T2.1-report.md
+```
+
+Workflow rule #5: *"Commit. One commit per task. Message: `T<id>: <one-line summary>`. The report file is part of the same commit."* Rule #6: status board → `Pending Review` comes AFTER the commit. The report shows `Commit: (see git log)` and no T2.1 commit exists in `git log`.
+
+**Rework (≤ 1 min):**
+
+1. Verify only T2.1's files are staged. The repo working tree also has earlier reviewer-note edits I made on `T1.6/T1.7/T1.8-report.md` — leave those alone; they're mine to commit separately if needed.
+2. `git commit -m "T2.1: Add SignalMessage::TransportFeedback"` over the currently-staged `Cargo.toml`, `Cargo.lock`, `packet.rs`, and `T2.1-report.md`.
+3. Fill in the real commit SHA in this report's header.
+4. Append a `## Rework — <UTC>` section noting "committed staged changes per rule #5".
+5. Move status back to `Pending Review`.
+
+**Why this matters:** "approved without a commit" leaves the work invisible to anyone pulling main and to the audit trail. Reviewers verify against `git log`; if `TASKS.md` and `git log` diverge, the workflow stops being legible.
+
+**Process correction for future tasks:** before flipping status to Pending Review, run `git status` — if any of your task's files show as modified or staged, you haven't committed yet.
+
+### Rework — 2026-05-11 (reviewer-completed)
+
+Agent committed the staged changes as `fe1f948` ("T2.1: Add SignalMessage::TransportFeedback") but did not append a Rework section to this report or move the board status back to Pending Review — they jumped straight to T2.2. I'm closing T2.1 retroactively because the substance was already approved and the commit exists.
+
+Commit `fe1f948` contents (5 files, 148 insertions, 2 deletions):
+- `Cargo.lock`, `crates/wzp-proto/Cargo.toml` — bincode dev-dep
+- `crates/wzp-proto/src/packet.rs` — `TransportFeedback` variant + 2 tests
+- `docs/PRD/TASKS.md`, `docs/PRD/reports/T2.1-report.md`
+
+Re-verified: `cargo test -p wzp-proto transport_feedback` (2 pass).
+
+### Reviewer notes (2026-05-11 — final)
+
+Approved. Substance was always fine. The workflow drift is being addressed via T2.2's review note (since T2.2 inherited the same workflow problem); see there for the firm-but-final rule #7 reminder.