#229 PR-1 — Discuss/Clarify spine: decision_messages + discuss() + decision_discuss MCP + pull union

You are being dispatched from flower Brief #258: #229 PR-1 — Discuss/Clarify spine: decision_messages + discuss() + decision_discuss MCP + pull union

Recall pointer:
- Use recall_brief with id 258 for the full folder if you need provenance.

Target:
- project: flower (/Users/mikeferrara/Documents/code/flower)
- branch: flower/258-discuss-spine
- worktree: not specified
- kind: fresh

Current brief spec:
(no spec yet)

This is a direct request, not a fully-specced plan. If it's clear, resolve it. If you hit a blocking ambiguity, call brief_ask (or brief_append) with your questions and flip the brief to `refining` before proceeding — don't guess.

Recent/key trace events:
[1] participant_joined flower-229-design: (no body)
[2] note_added flower-229-design: ## PR-1 — Discussion spine (child of #229; decisions epic #95)
Design: `docs/design/229-discuss-clarify-decision.md` §Service/§Thread-mechanism/§State-model. **Deps: none — dispatchable now.** Target ≤~300 lines, `php artisan test` green, `./vendor/bin/pint` clean.

The non-resolving back-end for operator↔daemon clarification on an OPEN decision. No UI in this slice.

### Build
- **Migration:** new `decision_messages` table `{id, decision_id (FK→decisions cascadeOnDelete), author_ref string, author_kind string(16), body text, timestamps}` (index `decision_id`); add `decisions.awaiting_turn` nullable `string(16)` (`null|operator|daemon`) + index. sqlite-portable (guard FKs off sqlite as the existing decision migrations do); verify up/down on MySQL.
- **Model** `DecisionMessage` (`$guarded=[]`) + `Decision::messages()` HasMany + `Decision::latestMessage()` (`HasOne … latestOfMany`, mirror `latestAnswer()` Decision.php:110) + scope `scopeAwaitingDiscussionReplyFor(string $canonicalRef)` = `where status=open AND awaiting_turn='daemon' AND assigned_to=ref` (mirror `scopeAwaitingAckFor` Decision.php:166-172).
- **`DecisionService::discuss(Decision $d, string $body, string $actorRef, string $authorKind): DecisionMessage`** — one tx: (1) **guard `status===Open`** (reject resolved/withdrawn — mirrors `openQuery()`); (2) write the message row; (3) set `awaiting_turn` to the counterparty (operator turn→`daemon`, daemon turn→`operator`); does NOT touch status/answer/answered_at/released_at/acked_at; (4) operator turn → `wakeAssignee($d)`, daemon turn → broadcast only; (5) dispatch `DecisionDiscussed`.
- **`answer()`/`withdraw()`**: add one line to null `awaiting_turn` on resolve (tidiness).
- **Parameterize `CoordinationQueue::enqueueDecisionWake`** with a `reason` (`'discuss'` vs the existing `'answered'`) so the wake payload message tells the daemon to reply, not ack (CoordinationQueue.php:92-118). Keeps the dedupe fingerprint distinct per reason.
- **Event `DecisionDiscussed`** — clone `DecisionAnswered` (ShouldBroadcast; `DecisionChannels::for($d)` → decisions + project.{id} + briefs.{id}; payload `RecallService::decisionSummary`).
- **MCP `decision_discuss`** tool (mutating, `actor_ref`-gated; register in `FlowerServer`) — input `{decision_id, body, actor_ref}`; derive `author_kind` (`operator:*`→operator; canonical `{project}-{role}`→daemon; else reject); calls `discuss()`.
- **Pull:** extend `pullFor()`/`recall_decisions` to UNION `awaitingDiscussionReplyFor(canonical)` with the existing `awaitingAckFor` (disjoint: released vs open); `decisionPayload` (SerializesDecisions.php) gains `awaiting_turn` + bounded `messages[]` (last 20). **Update the `recall_decisions` tool Description** to branch on `awaiting_turn` (reply via decision_discuss vs ack).

### Tests
discuss writes a non-resolving row, does NOT release/resolve, flips `awaiting_turn`, fires a wake ONLY on the operator turn; discuss on a resolved/withdrawn call is rejected; a `system:*` author_kind is rejected; `recall_decisions` surfaces awaiting-my-reply with the thread + `awaiting_turn`; resolve-once answer + ack paths unchanged (regression); `enqueueDecisionWake` reason distinguishes discuss vs answered.

### Activation note
Standing daemons pick up the new reply loop only after a reset onto fresh code (orchestrator schedules `flower:daemon-schema-reload` after merge). A pre-feature daemon that acks an open discuss call hits the guarded `ack()` no-op — harmless.
[3] parent_set flower-229-design: Grouped under epic #229.
[4] status_change flower-229-design: (no body)

Recommended linked context:
{
    "todos": [],
    "scratchpads": []
}

Execution notes:
- Treat the brief as the source of truth.
- Keep work scoped to this dispatch request.
- Use brief_append / brief_update_status when reporting material progress; as your final dispatched-worker step, call brief_dispatch_complete with dispatch_request_id (or brief_id) and actor_ref.
- Codex workers should verify mutating Flower tools with tool_search query `brief_append brief_dispatch_complete flower_feedback` (limit 20) when tool availability is in doubt; report raw SEE/LOAD vs NOT visible instead of silently using local fallbacks.
- Add a git commit trailer `Brief: #258` to every commit for this brief so flower can exact-link commits back to the brief.
- Need an operator call while working this brief? A question ABOUT THIS BRIEF -> brief_ask(258, ...); a standalone decision not tied to the brief -> decision_ask(...). Both expose the full affordance set (confirm | single_choice | multi_choice | text, options + recommended, allow_write_in); prefer async questions over blocking and set is_blocking only when you truly cannot proceed.
- Cited-refs index (Brief #244): when a report / checkpoint / DONE summary cites numbered entities, append a compact `Refs:` block at the END mapping each `#N` to its REAL stored title + status — `#<num>: <title> (<status>)`, one per line (typed prefixes: bare `#N` = brief, `fb#N` feedback, `dec#N` decision, `sess#N` session, `dr#N` dispatch_request). Resolve any title you did not already pull with recall_refs instead of guessing; skip the block on trivial one-liners.