feat: custom message types for system turns — wake and verdict messages

The custom-message scheme (user-decided 2026-09-12): system-authored
user-role messages are NOT human messages — they carry marker data parts
only, the adapter owns their model-facing wording, and the UI renders
them under control. Nothing fake is ever persisted as human speech.

The inventory (all migrated):
- probe→teacher handoff wake: was a text-bearing user message rendering
  as a fake user bubble; now data-probe-handoff marker-only — the
  adapter flattens it to HANDOFF_TEXT (core/contracts/chat.ts), the UI
  renders a quiet 'Preparing your plan…' system line.
- plan accept/decline: was boilerplate text ('The plan is accepted…',
  'I'd like the plan revised…') masquerading as learner speech — the
  decline wasn't even marked; now data-verdict {accepted, at} on its own
  message, adapter flattens to verdictText(), UI renders the quiet
  verdict marker ('✓ Plan accepted' / '↻ Plan revision requested').
  sendVerdict sends TWO REAL MESSAGES when the learner typed a note
  (the note as a genuine user message, then the verdict) in ONE turn
  via setMessages + sendMessage() — no 409 dance, no double teacher turn.
- sub-agent steers: the abort steer gains its data-subagent-aborted
  marker part; the UI keys steer rendering off PARTS (artifact/aborted),
  not metadata — metadata stays as pump mechanics only.
- record-adapter: systemTextOf() flattens marker-only messages; steers
  keep their text (payload — briefs are content, not boilerplate).

phases.ts: plan→teach advances on data-verdict{accepted:true} only;
learner text alone can never sanction teaching (pinned). data-plan-
accepted retired, no back-compat (user-decided: wiped-data doctrine).

Pinned: record-adapter.test.ts (verdict/handoff flattening, note+verdict
order, steer payload kept, UI-only parts skipped), phases.test.ts
(verdict marker semantics, out-of-order, text-never-fakes), jobs.test.ts
(abort marker part), demos.test.tsx (badge renders off the part, not
metadata).

Live GLM smoke (disposable driver, deleted): probe→conclude→wake→plan→
decline-with-note (revised, still plan)→accept-with-note (teach) — ALL
CHECKS PASS, including marker-only handoff/verdict on the wire and zero
fake human speech in the transcript.

Gates: tsc, lint, build, 335/335.

src/server/pi/record-adapter.ts

@@ -1,6 +1,7 @@
 import type { UIMessage } from "ai";
 import type { AgentMessage } from "@earendil-works/pi-agent-core";
 import type { AssistantMessage, Message, ToolResultMessage } from "@earendil-works/pi-ai";
+import { HANDOFF_TEXT, verdictText } from "../../core/contracts/chat.ts";
 
 /**
  * The record → pi-ai transcript adapter (docs/pi-engine-swap.md §4). The
@@ -8,9 +9,15 @@ import type { AssistantMessage, Message, ToolResultMessage } from "@earendil-wor
  * fresh agent from it (the stateless per-turn decision). This replaces the
  * SDK's convertToModelMessages with an owned, explicit mapping:
  *
- * - user text parts → UserMessage text content; data parts are dropped
- *   (the plan-accept seam rides its text twin — the client always sends
- *   "The plan is accepted — begin teaching." alongside the marker).
+ * - user text parts → UserMessage text content.
+ * - SYSTEM DATA PARTS (the custom-message scheme, 2026-09-12): the wake and
+ *   verdict messages carry ONLY a marker part — no human text exists to
+ *   drop, so the ADAPTER flattens them: data-verdict → verdictText(),
+ *   data-probe-handoff → HANDOFF_TEXT (core/contracts/chat.ts owns both —
+ *   single source, so the model-facing wording can't drift from the seam).
+ *   Other data parts (artifacts, plan blocks) are dropped as before: they
+ *   are UI history; the steer briefs ride their text twin (payload, not
+ *   boilerplate — those texts are content the sub-agent produced).
  * - assistant text/reasoning/tool parts → one AssistantMessage whose
  *   content blocks mirror the part order; tool parts become ToolCall
  *   blocks (output-error parts keep their rawInput).
@@ -46,6 +53,18 @@ function zeroUsage() {
 	};
 }
 
+/** The model-facing text of a marker-only user message, or null when the
+ *  message has no model face at all (UI-only data parts). */
+function systemTextOf(parts: ReadonlyArray<{ type: string; data?: unknown }>): string | null {
+	for (const part of parts) {
+		if (part.type === "data-verdict") {
+			return verdictText((part.data as { accepted?: unknown } | undefined)?.accepted === true);
+		}
+		if (part.type === "data-probe-handoff") return HANDOFF_TEXT;
+	}
+	return null;
+}
+
 export function recordToPiMessages(messages: UIMessage[]): Message[] {
 	const out: AgentMessage[] = [];
 
@@ -55,7 +74,15 @@ export function recordToPiMessages(messages: UIMessage[]): Message[] {
 				.filter((p) => p.type === "text")
 				.map((p) => textOf(p as { text?: string }))
 				.filter((t) => t.length > 0);
-			if (texts.length === 0) continue; // pure data-part marker, no text
+			// The custom-message scheme: a marker-only message (verdict,
+			// handoff) flattens to its canonical model-facing text — the
+			// wording lives in the adapter's reach (core contracts), never
+			// authored as fake human speech in the transcript.
+			if (texts.length === 0) {
+				const flat = systemTextOf(message.parts);
+				if (flat === null) continue; // pure UI data part, no model face
+				texts.push(flat);
+			}
 			out.push({
 				role: "user",
 				content: texts.map((text) => ({ type: "text" as const, text })),