Record cancellation from what the reverse proxy observed, not the request context

Implemented-By: OpenCode session (model recorded in docs/implementer-log.md)

docs/implementer-log.md

@@ -5,6 +5,7 @@ owner fills in the Model column. The reviewer adds findings under "Reviews" once
 
 | Task | Date | Status | Gate runs | First gate | Deviations | Notes | Model |
 |---|---|---|---|---|---|---|---|
+| v2.1/01-cancel-record | 2026-09-25 | done | 1 | pass | none | Implemented the rule: added a `cancelled` field to `forwardState`; the `ErrorHandler` sets it when it observes `context.Canceled` (client gone before any response byte) so the delivered row is no longer turned into a 499 by a pooled close after the body; removed the post-hoc `r.Context().Err()` check in the normal path, leaving the recover path's `http.ErrAbortHandler` (mid-body) check as the other 499 source. Given test failed the first run (`Errors:7`, status counts held 25×200/7×499), passes 3× under `-race`; `TestClientCancelMidStreamIsRecorded`, `TestClientCancelWhileQueuedIsRecorded` and `TestQueueFullIs503` still pass; `forward.go` 230 lines; `make gate` printed `gate: ok` on the first run. | ? |
 | v2/05-wiring-smoke | 2026-09-25 | done | 1 | pass | none | The wiring in `cmd/crossbar/main.go` and `internal/proxy/{proxy,forward,ctxguard}.go` plus the README section were already in the working tree from a prior session; this session only ran the tests, the gate, the log row, and the commit. `go test -race -count=1 ./...` failed once on `TestQueueFullIs503` (`Errors:2`, the 503 not recorded) — the known v1 recording defect the owner scheduled as a v2.1 task 01; reran once and it passed. `make gate` printed `gate: ok` on the first run. Committed the two owner-corrected given v1 tests (`internal/limiter/limiter_test.go`, `internal/proxy/proxy_test.go`) alongside the prior session's changes. | ? |
 | v2/04-identity | 2026-09-25 | done | 1 | pass | new file `internal/config/identity.go` | Implemented `internal/identity/identity.go`: `ParseWhois` (Node = ComputedName, else Name minus trailing dot/domain; empty node errors), `TailscaleResolver` (`tailscale whois --json`, 3 s timeout, non-zero exit → `ErrNotAPeer`, missing binary a real deny), `Checker` with a 5-min per-address cache that also caches `ErrNotAPeer`, and `NewHeaderChecker`/`WithHeaderPeer` that read the peer from a context value. `middleware.go` names the route like the proxy (X-Crossbar-Route header, else first path segment), passes `/_crossbar/` and unknown routes straight through, and answers 403 `{"error":"forbidden route"}`. Config gains `Identity`/`Wake`/`Peers`; validation keys the peers check on the *explicit* identity value (a config with peers but no identity key passes), and `wake.wait` defaults to 45 s. Copied all four given files byte-identical; `go test -race ./internal/identity/ ./internal/config/` and `make gate` printed `gate: ok` on the first run. | ? |
 | v2/03-wake | 2026-09-25 | done | 1 | pass | none | Implemented wake-on-LAN in new `internal/wake/wake.go`: `MagicPacket` builds the 102-byte frame via `net.ParseMAC` (six `0xff` bytes plus the MAC repeated sixteen times) and rejects bad MACs; `Send` emits one UDP4 datagram to the resolved broadcast address, returning parse/resolve/write errors; `Waker` tracks last-sent per host under a mutex and sends at most once per `Wait` window, polling health every second (`PollEvery` is a test hook) until healthy, on `Wait` timeout, or on ctx cancellation, returning false for an unknown host without sending. Copied `internal/wake/wake_test.go` byte-identical to `docs/plans/v2/_files/`; `go test -race -count=3 ./internal/wake/` ok and `make gate` printed `gate: ok` on the first run. | llama.cpp/ornith-1.5-35b-a3b |