qwen3.5 executor + continuation primitive + think:false

Three coupled fixes that together turned the Riverfront Steel scenario
from 0/5 (mistral) to 4/5 (qwen3.5) with T3 flagging real staffing
concerns rather than linter advice.

MODEL SWAP
- Executor: mistral → qwen3.5:latest (9.7B, 262K ctx, thinking).
  mistral's decoder emitted malformed JSON on complex SQL filters
  regardless of prompt; J called it — stop using mistral.
- Reviewer: qwen2.5 → qwen3:latest (40K ctx)
- Applied to scenario.ts, orchestrator.ts, network_proving.ts,
  run_e2e_rated.ts

CONTINUATION PRIMITIVE (agent.ts)
- generateContinuable(): empty-response → geometric backoff retry;
  truncated-JSON → continue from partial as scratchpad; bounded by
  budget cap + max_continuations. No more "bump max_tokens until it
  stops truncating" tourniquet.
- generateTreeSplit(): map-reduce for oversized input corpora with
  running scratchpad digest, reduce pass for final synthesis.
- Empty text no longer throws — it's a signal to continuable that
  thinking ate the budget.

think:false FOR HOT PATH
- qwen3.5 burned ~650 tokens of hidden thinking for trivial JSON
  emission. For executor/reviewer/draft: think:false. For T3/T4/T5
  overseers: thinking stays on (that's the point).
- Sidecar generate endpoint accepts `think` bool, passes through to
  Ollama's /api/generate.

VERIFIED OUTCOMES
Riverfront Steel 2026-04-21, qwen3.5+continuable+think:false:
  08:00 baseline_fill  3/3  4 turns
  10:30 recurring      2/2  3 turns (1 playbook citation)
  12:15 expansion      0/5  drift-aborted (5-fill orchestration
                            problem, separate work)
  14:00 emergency      4/4  3 turns (1 citation)
  15:45 misplacement   1/1  3 turns
  → T3 caught Patrick Ross double-booking across events
  → T3 flagged forklift cert drift on the event that failed
  → Cross-day lesson proposed "maintain buffer of ≥3 emergency
    candidates, pre-fetch certs for expansion, booking system
    cross-check" — real staffing advice, not generic linter output

PRD PHASE 21 rewritten to reflect the actual primitive shape (two-
call map-reduce with scratchpad glue) instead of the tourniquet
approach originally documented. Rust port queued for next sprint.

scripts/ab_t3_test.sh: A/B harness that chains B→C→D runs and emits
tests/multi-agent/playbooks/ab_scorecard.json.

tests/multi-agent/network_proving.ts

@@ -49,8 +49,8 @@ import {
   callTool,
 } from "./agent.ts";
 
-const EXECUTOR_MODEL = "mistral:latest";
-const REVIEWER_MODEL = "qwen2.5:latest";
+const EXECUTOR_MODEL = "qwen3.5:latest";
+const REVIEWER_MODEL = "qwen3:latest";
 const VERIFIER_MODEL = "qwen2.5:latest";
 const PROFILE_ID = "staffing-recruiter";
 const INDEX_NAME = "workers_500k_v1";
@@ -175,7 +175,7 @@ async function buildPhase(task: TaskSpec, prefix: string): Promise<BuildResult>
     while (turn < MAX_TURNS && !sealed) {
       turn += 1;
 
-      const execRaw = await generate(EXECUTOR_MODEL, executorPrompt(task, log), { temperature: 0.2, max_tokens: 600 });
+      const execRaw = await generate(EXECUTOR_MODEL, executorPrompt(task, log), { temperature: 0.2, max_tokens: 1200 });
       const execAction = parseAction(execRaw, "executor");
       append({ turn, role: "executor", model: EXECUTOR_MODEL, kind: execAction.kind as any, content: execAction });
 
@@ -192,7 +192,7 @@ async function buildPhase(task: TaskSpec, prefix: string): Promise<BuildResult>
         }
       }
 
-      const revRaw = await generate(REVIEWER_MODEL, reviewerPrompt(task, log), { temperature: 0.1, max_tokens: 400 });
+      const revRaw = await generate(REVIEWER_MODEL, reviewerPrompt(task, log), { temperature: 0.1, max_tokens: 1000 });
       const revAction = parseAction(revRaw, "reviewer");
       append({ turn, role: "reviewer", model: REVIEWER_MODEL, kind: "critique", content: revAction });