docs(api): pass admin list parameters in a JSON body (15.9)

[marevol]

Summary

The 15.9 Admin API pages had curl examples that passed list parameters in the URL query string, such as ?size=50&page=1, ?errorCountMin=3, ?sessionId=... and ?q=Fess. Those endpoints read their parameters only from a JSON request body with snake_case keys, so the examples did nothing. Two of them misbehaved:

• GET /api/admin/searchlist/docs?q=Fess searched every document.
• DELETE /api/admin/searchlist/query?q=... returned an error, because q was empty.

Changes

All seven locales, 15.9 only:

• curl examples. The 15 examples in each locale now send a JSON body with -X GET/-X DELETE, Content-Type: application/json and -d. The keys are snake_case, for example {"error_count_min": 3} and {"session_id": "..."}.
• Admin API overview. A note under the list pagination parameters says they, and each resource's filter parameters, go in a JSON body with snake_case keys, and that the query string is ignored.
• jq filters. The joblog examples now filter on .job_status instead of .jobStatus, which the snake_case response no longer has.
• Comment. The failureurl example comment now names error_name.

Verification

Each rewritten example was run against a 15.9 snapshot. For comparison:

• On role/settings, ?size=2&page=2 returned the first page; the same values in a body returned the second.
• On failureurl/logs, {"error_count_min": 3} filtered the results; {"errorCountMin": 3} and ?error_count_min=3 did not.

The session_id, error_name, owner, searchlist q and joblog jq examples were also checked. tools/check_headings.py reports nothing for 15.9.