Agent run persistence and a durable event stream

Context

A run of the tool-calling agent loop (ToolLoopService::runLoop()) existed only for the lifetime of one HTTP request. It returned a ToolLoopResult value object and was then gone. The only inspectable trace, RunTrace, is an in-memory collector the admin playground builds to stream steps to the browser; nothing was written to storage.

That is the missing foundation under every larger agent capability: a run cannot be resumed after a worker restart, queued for later execution, paused for a human approval, audited, or replayed by a consumer UI, because there is no persisted run to attach any of that to. Cross-call usage already carried a correlation_id (tx_nrllm_telemetry), but nothing promoted it into a first-class run.

Decision

Persist each run and its steps in two UI-less log tables, tx_nrllm_agentrun (one summary row per run) and tx_nrllm_agentrun_event (one row per recorded step, ordered by sequence). Both follow the telemetry precedent (ADR-058): raw Doctrine access through AgentRunRepository, no Extbase model and no TCA, because a run log is written and read programmatically, never edited in FormEngine.

Drive persistence from the existing `RunTrace.onRecord` hook. A fail-soft AgentRunPersister opens a run (begin() → RUNNING), records each RunStep as an event as it is emitted (recordStep()), and settles the run to a terminal state (settleCompleted() / settleFailed()). The tool loop is not touched: the persister is wired through the same per-step callback the playground already uses to stream steps, so the loop's control flow is unchanged and unaware of it.

Type the vocabulary without inventing what the loop cannot emit. AgentRunStatus carries the full lifecycle the later epics need (queued, running, waiting_for_approval, waiting_for_input, completed, failed, cancelled), but this change only ever writes RUNNING → COMPLETED/FAILED. AgentEventKind is limited to the four kinds RunStep actually produces (request, llm, tool, assembled); richer kinds are added by the epics that emit them.

Fail-soft is a hard requirement. Every persister method logs and swallows a storage error; begin() returns null on failure, which the caller treats exactly as a null RunTrace callback — "record nothing". A database hiccup can therefore never break an otherwise-successful run. The streamed path settles the run in a finally block (mirroring StreamingDispatcher), so a client disconnect mid-stream cannot leave a run stuck RUNNING.

Consequences

• Playground runs (batch and streamed) now persist. The admin playground is the first consumer; the tables are the substrate the human-in-the-loop, batch/queue and feedback epics build on.

• A run that exhausts its iteration cap or is denied by the budget guard both surface as COMPLETED with truncated = true, because ToolLoopService catches the budget denial internally and returns a normal result. Recording a budget denial as a distinct FAILED run is deferred to the human-in-the-loop epic, which reshapes the loop's exit paths.

• Event payloads store the full RunStep snapshot, which includes the messages sent (the prompt). AgentRunRepository::purgeOlderThan() provides the retention hook; a scheduled purge command is a follow-up. Runs are admin-authored for now (the playground is admin-only), so the exposure is limited.

• The persister depends on AgentRunRepositoryInterface, so it is unit-tested against a recording double; the raw SQL and schema are covered by a functional round-trip.