M3a spec: fold in area E's findings; runbook and egress to match

Every request is recorded, unreadable state is recorded as secret, a
refusal that cannot be recorded is an error, and the other cases the
brokerd reference settled. The audit-unavailable and
broker-state-damaged entries name the new messages; egress lists the
development calls to straylight.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

docs/decisions.md

@@ -6,6 +6,7 @@ Newest first. A decision that changes `docs/design.md` lands in the same commit
 
 | Date | Decision | Reason |
 |---|---|---|
+| 2026-09-18 | M3a plan checks, `brokerd`. Every tool request gets a `Decision` record, including those denied `grants_invalid` or `state_unreadable`; forbidden kinds get none. An unreadable session state is recorded as `secret`, untrusted. A refusal that cannot be recorded is `error internal`, not `ok`. The re-decision's outcome is the matched grant's mode. A pending frame that cannot be sent is handled like a lost connection. Expiry lives in `admin`. A request frame without a read timeout is accepted for M3a. | Found while writing the reference for tasks 10 to 15: the spec left each case open, and `bxctl refuse` would have reported success for a refusal that was not on disk. |
 | 2026-09-18 | M3a plan checks, audit. `DecisionRecord::Allowed {}` and `Ask {}` are empty struct variants. The resumed verifier accepts a break naming an older file inside a failed region too. When the previous file's last line does not parse, an ordinary start verifies the whole log. A `Recovery` that describes no line is a failure. `abandoned` and `unfinished` both name the decision's `seq`. The report carries what a `Recovery` or `AcceptedBreak` must hold. `--accept-break` with nothing to accept writes nothing. | serde ignores `deny_unknown_fields` on unit variants of an internally tagged enum, so `{"outcome":"allowed","x":1}` decoded; found by `strict.rs` in two areas, and the struct-variant fix was kept over a hand-written `try_from` as the smaller one that also refuses `"reason":null`. As specified, a correctly accepted break could stop every later start while `--accept-break` said "nothing to accept". |
 | 2026-09-18 | M3a plan checks, policy and `loopd`. A host name's last label starts with a letter. For `write_file` a grant path equal to the argument does not count toward the match. `redecide` returns `Result<Decision, Denial>`, and `Denial` carries the `deny` grant and its hash. `BrokerPort`'s waits are deadlines, not per-read timeouts; the envelope id is `request.call.0`. `approval_pending.tool` and `tool_denied.name` are the target tool, not `call_tool`. `echo` stays in the test registry. | `127.0.0.1` and `127.1` fitted the host grammar, so "no IP literals" was false. A per-read timeout let a trickling peer hold a turn for ever. `call_tool` tells the owner nothing. |
 | 2026-09-18 | M3a plan checks, `bxctl` and the runbook. A runbook anchor must be written out in the source, and the check fails when it finds no pointer. `--say` shows the approval block and does not ask; `--json` prints only the event and never contacts `brokerd`. Everything the model wrote is escaped, tool names and the final answer included. The approval list shows arguments in `serde_json`'s compact form. | A computed anchor could not be checked. "Print the event only" had no meaning without `--json`. The spec's example contradicted section 6. |