Some @anthropic-ai/claude-agent-sdk versions throw from the query
generator when maxTurns is reached, instead of emitting a result
message with subtype='error_max_turns'. The runner treated that as
a non-retryable error and killed the whole periodic run on the first
fixture that exceeded its turn cap.
Added isMaxTurnsError() detector and a catch branch that synthesizes
an AgentSdkResult from events captured before the throw, with
exitReason='error_max_turns' and costUsd=0 (unknown from the thrown
path). The metric function still runs against whatever assistant
turns were collected, so the trial produces a usable number.
Hoisted events/assistantTurns/toolCalls/assistantTextParts and the
timing counters out of the inner try so the catch branch can read
them. No behavior change on the success path or on rate-limit retry
paths.
`test/helpers/agent-sdk-runner.ts` wraps @anthropic-ai/claude-agent-sdk
with explicit `AgentSdkResult` types, process-level API concurrency
semaphore, and 3-shape 429 retry (thrown error, result-message error,
mid-stream SDKRateLimitEvent). Pins the local claude binary via
`pathToClaudeCodeExecutable`.
`test/fixtures/overlay-nudges.ts` holds the typed registry. Two
fixtures for the first measurement: `opus-4-7-fanout-toy` (3-file read)
and `opus-4-7-fanout-realistic` (mixed-tool audit). Strict validator
rejects duplicate ids, non-integer trials, unsafe overlay paths, non-safe
id chars, and missing overlay files at module load.
Adding a future overlay nudge eval = one fixture entry.
