Add run-scoped ingestion policy and budget admission

[JSv4]

Remote-ingest admission currently limits queue backlog, and local checkpoints fingerprint preparation settings. Neither provides a server-enforced run policy or expenditure ceiling covering asynchronous processing and retries.

Implementation

• Introduce a durable ingestion-run identity with an immutable, secret-free policy snapshot: permitted processing stages/providers, parser/embedder/model identities and dimensions, allowed fallback behavior, and a configurable monetary ceiling with a versioned pricing/estimation basis.
• Bind uploads and resulting asynchronous work to the run. Validate the effective configuration at execution as well as admission; a global settings change must not silently select a different or unapproved provider.
• Reserve a conservative cost bound atomically before chargeable work is admitted. Include queued/in-flight work, retries, and downstream actions; reconcile reservations against accounted usage without double charging on task redelivery.
• When the next operation cannot fit the remaining budget, stop admitting it and expose a resumable budget-exhausted state. Unknown/unbounded costs must not be treated as zero; define how external worker preparation is reserved/reported or explicitly excluded from the guaranteed coverage.
• Expose authorized run totals, reservations, remaining allowance, policy violations, and pause/resume status through the API and CLI. Keep credentials out of snapshots and reports.
• Reuse pipeline resolution, checkpoint identities, and queue admission. Document exactly which costs are bounded; do not present estimates as a guarantee of an entire infrastructure bill.

Acceptance criteria

• Concurrent admissions cannot exceed the configured ceiling through competing reservations.
• Tests cover exact-boundary rejection, retries/redelivery, crashes with outstanding reservations, cancellation, unknown pricing, configuration changes, and prohibited fallback.
• Budget exhaustion preserves receipts/checkpoints, and status separates accounted usage from reservations and estimates.
• No downstream chargeable stage escapes the declared run policy.

Related: #2318 provides preparation identities; #2319 provides backlog admission, which remains a separate limit.

Code pointers

admission governor; checkpoints; worker processing; pipeline settings API; document-triggered work.