[docs-patrol] Document new osquerybeat scheduled-query metadata fields in exported fields docs

Recent code changes introduced documentation drift for `osquerybeat` exported fields.

## Changes Requiring Documentation Updates

### 1. New scheduled-query metadata fields are emitted but not documented

**Commit(s):**
- `3a992dbf4f45e25dcc3b2afd3ccd1a713c3ad732` (`feat(osquerybeat): improve native scheduled-query metadata and identifiers`)

**What changed (code evidence):**
- `x-pack/osquerybeat/beater/osquerybeat.go:545-548` now adds `planned_schedule_time` and `schedule_execution_count` to query result metadata.
- `x-pack/osquerybeat/internal/pub/publisher.go:165-182` now emits `schedule_id`, `planned_schedule_time`, `schedule_execution_count`, and optional `pack_id` / `space_id` in scheduled response events.

**Documentation impact (current docs evidence):**
- `x-pack/osquerybeat/_meta/fields.yml:1-4` is still empty (`fields:` has no definitions).
- `x-pack/osquerybeat/docs/fields.asciidoc:15621-15624` still says `== Osquerybeat fields` followed by `None`.

This makes current exported-fields documentation concretely incorrect for users inspecting osquerybeat event schema.

## Suggested Actions

- [ ] Add osquerybeat field definitions for the newly emitted scheduled-query metadata fields in `x-pack/osquerybeat/_meta/fields.yml` (at minimum: `planned_schedule_time`, `schedule_execution_count`, and any other newly emitted top-level scheduled response fields that are intended to be public).
- [ ] Regenerate/update `x-pack/osquerybeat/docs/fields.asciidoc` so `Osquerybeat fields` no longer reports `None` for these emitted fields.
- [ ] Confirm whether `pack_id` / `space_id` in scheduled responses are intended public fields; if yes, document them in exported fields as well.

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> - [x] expires on Mar 24, 2026, 2:41 PM UTC

Start with x-pack/osquerybeat/_meta/fields.yml and review the emitted fields in x-pack/osquerybeat/beater/osquerybeat.go:545-548 and x-pack/osquerybeat/internal/pub/publisher.go:165-182. Add definitions for the intended scheduled-query metadata fields, clarify whether pack_id and space_id are public, then regenerate x-pack/osquerybeat/docs/fields.asciidoc. Done means the generated Osquerybeat fields section documents the emitted fields instead of reporting None.

Written by the indexing model from the issue text.