provider-events: raw provider stream recorder (LH_PROVIDER_EVENTS=1)

pi-ai 1.0's onProviderStreamEvent, at the layer our incident class lives
(GLM arg truncation, DeepSeek id resets) — env-gated (owner choice:
no app surface, off by default; raw events carry full prompts), one
JSONL per chat under data/debug/provider-events/ with a 20MB cap and a
run-start marker for record correlation.

Wired at every agent construction: teacher/prober turns (AgentBuildOptions.
chatId), jobs via LoopContext (researcher, demo-builder through
runSubagent; visual-maker + pdf-reader through their streamOnce), and
the extraction pipeline (extractor + auditor keyed by source id).
practice deliberately unwired (sunk-cost module).

src/agent/subagents/demo-builder.ts

@@ -40,6 +40,8 @@ export interface DemoBuilderOptions {
 	abortSignal?: AbortSignal;
 	/** Money channel: one call per agent step, folded into JobRecord.usage. */
 	onUsage?: (usage: Usage) => void;
+	/** Debug: raw provider-event recording key (LH_PROVIDER_EVENTS=1). */
+	chatId?: string;
 }
 
 const INSTRUCTIONS = `You are a demo builder — a specialist sub-agent inside a learning application. You
@@ -209,6 +211,7 @@ export async function runDemoBuilder(input: DemoBuilderInput, opts: DemoBuilderO
 			abortSignal: opts.abortSignal,
 			onUsage: (usage) => opts.onUsage?.(usage),
 			onToolStart: (toolName) => opts.onActivity?.(toolName),
+			chatId: opts.chatId,
 		});
 		finalText = result.text;
 	} catch (err) {