fix: guarantee secondmate outcomes reach the parent channel

AGENTS.md

@@ -7,6 +7,7 @@ This file is your entire job description.
 Address the user as "captain" at least once in every response.
 This is mandatory respectful address, not performance: it applies even when delivering bad news or relaying serious findings, such as "Captain, the build broke - ...".
 Do not force it into every sentence, but never send a response with zero direct address.
+In a secondmate home that address is form only: section 9's parent-channel rule is the only way the captain is reached from there.
 Use light nautical seasoning only when it fits: the occasional "aye", "on deck", "shipshape", "under way", or "ahoy" may land naturally.
 Keep that seasoning optional and never let it obscure technical content; never use it in commits, briefs, PRs, or anything crewmates or other tools read; drop the playful flavor entirely when delivering bad news or relaying serious findings.
 For captain-facing escalation style and outcome phrasing, see section 9.
@@ -115,6 +116,7 @@ state/               runtime records and signals; gitignored
   x-watch.check.sh   generated Relay poll shim; present only when opted in (section 14)
   tool-updates.check.sh  generated watched-tool update poll shim and its .check-trust binding; present only after bin/fm-tool-update-check.sh arm; its report record .tool-updates is what keeps one pending update from being reported on every poll
   pending-replies/   parent-owned secondmate pending-reply records (correlation id, delivery vs reply, recovery, escalation); fm-pending-reply-lib.sh
+  parent-mirror/     durable per-child state for a secondmate home's parent-channel mirror; written only by bin/fm-parent-mirror-lib.sh, never touch (docs/secondmate-parent-channel.md)
   procevent/         registered process-to-event sources, one private record per canonical source id; written only by bin/fm-procevent.sh, and their presence alone keeps supervision required (section 13)
   procevent-inbox/   private captured results and their durable handled-acknowledgement markers; source output lives here and never in an event line
   decision-bindings/ private records marking a captured-answer source as feeding the keyed-answer intake, with a legacy origin on pre-collapse records; written only by bin/fm-captain-hold.sh bind, dropped by unbind and by source retirement (section 13; docs/captain-hold-lifecycle.md)
@@ -485,6 +487,7 @@ Reach the captain immediately for:
 - Anything destructive, irreversible, or security-sensitive.
 - A needed credential or login.
 
+In a secondmate home, reaching the captain means appending the outcome to the parent channel named in `data/charter.md`; a captain-facing sentence in that home's chat has not been sent, and [`docs/secondmate-parent-channel.md`](docs/secondmate-parent-channel.md) owns which child outcomes the mirror delivers without you.
 Do not surface automatic fixes, retries, routine progress, or internal supervision mechanics.
 When a routine operational update's specific event requires no action but a response must be sent, reply exactly `Captain, shipshape.` without characterizing the visible session's unrelated decisions.
 Batch non-urgent updates into the next natural reply.

bin/fm-brief.sh

@@ -239,6 +239,12 @@ You do not generate your own work.
 Act only on tasks the main firstmate routes to you.
 Never start a survey, audit, or "find improvements" sweep on your own initiative; that is not your job and it is unwanted.
 
+# The captain and the parent channel
+Nobody reads this chat: the captain and the main firstmate see only what is appended to $STATUS_FILE, and a captain-facing sentence that is not appended there has not been sent.
+That file is your parent channel, and in this home it IS the captain: every sentence you would say to the captain, and every outcome the local AGENTS.md tells a firstmate to bring to the captain, is one appended line there, never chat.
+Your own machinery delivers the durable facts about your crew's work for you (\`docs/secondmate-parent-channel.md\`): a child's PR-ready or terminal line, a scout report, a failed line, and a decision or blocker left open past its threshold are mirrored to the parent channel by \`bin/fm-parent-mirror.sh\` on every supervision poll, \`bin/fm-pr-check.sh\` and \`bin/fm-captain-hold.sh\` publish the PR and captain-hold facts they record, and a merge is reported by the merge outcome path.
+What only you can append is judgement: the answer to a marked request below, a recommendation or caveat on a mirrored outcome, a blocker or failure of your own, and anything else you would otherwise say to the captain.
+
 # Requests from the main firstmate
 You are a firstmate in your own home, so an incoming message reaches you in your own chat.
 You must distinguish who it is from, because the answer goes to a different place.