fix: re-derive the turn number from the log at turn open

An out-of-band zero-step turn (durable command lifecycle on an idle log)
advances the log's turn numbering behind ReactLoopAgent's cached lastTurn,
so the next real turn reused a stale number and tripped the session
invariant (turn/start expected N, got 1) — hanging the TUI after any idle
slash command. The log is the numbering authority: take max(cached, logged)
+ 1 at open. The command-goal stub's inject helper also gains the one-shot
injection turn wrap the real agent performs, restoring turn enclosure in
its log assertions.

packages/core/agent-loop/src/agent.ts

@@ -312,7 +312,11 @@ export class ReactLoopAgent implements Agent {
     this.abort = controller
     this.acceptsNextStep = true
     const signal = controller.signal
-    const turn = this.lastTurn + 1
+    // The log is the turn-number authority: out-of-band zero-step turns
+    // (command lifecycle on an idle log) advance it behind this cached
+    // counter, so re-derive the successor at open instead of trusting it.
+    const loggedLast = this.session.events.findLast(event => event.type === 'turn/start')?.data.turn ?? 0
+    const turn = Math.max(this.lastTurn, loggedLast) + 1
     let step = 0
     let opened = false
     let reason: TurnEndReason = { kind: 'completed' }

packages/goal/command-goal/tests/command-goal.spec.ts

@@ -16,9 +16,13 @@ interface Harness {
   readonly plugin: Awaited<ReturnType<Context['plugin']>>
 }
 
-/** Append one idle injection using the public Agent contract. */
+/** Append one idle injection using the public Agent contract (idle inject wraps in a one-shot injection turn, per turn enclosure). */
 function appendInjection(session: Session, input: UserMessageData): void {
+  const lastStart = session.events.findLast(event => event.type === 'turn/start')
+  const turn = (lastStart?.data.turn ?? 0) + 1
+  session.append('turn/start', { turn, trigger: { kind: 'injection', source: input.source } })
   session.append('user/message', input, { surfaceOp: 'append' })
+  session.append('turn/end', { turn, reason: { kind: 'completed' } })
 }
 
 /** Build a live idle agent accepted by the exact-identity goal service. */