docs: document file search result limits

[HAYDEN-OAI]

Summary

• add an Assistants helper example for configuring max_num_results
• document the exact run-level path: tools[].file_search.max_num_results
• clarify that message attachments only associate files with file_search and cannot carry tool configuration

Why

Issue #1004 reports conflicting guidance about where max_num_results belongs. The generated Assistants types already expose the correct run-level shape, but the hand-maintained helper guide did not show it or contrast it with the invalid attachment placement.

Impact

Existing Assistants users now have a copyable example for limiting file search results without changing the generated API surface or runtime behavior.

Validation

• pnpm run format
• pnpm run lint

Resolves #1004

[openai-sdks]

OkTest Summary

✅ 237/237 SDK tests passed in 10.41s for Node SDK PR #1981.

Test results — 42 files

Test	Result	Time
tests/chat-completions-complex-body.test.ts	✅ Passed	148ms
tests/chat-completions-create.test.ts	✅ Passed	212ms
tests/chat-completions-stream.test.ts	✅ Passed	212ms
tests/files-content-binary.test.ts	✅ Passed	142ms
tests/files-create-multipart.test.ts	✅ Passed	142ms
tests/files-list-pagination.test.ts	✅ Passed	163ms
tests/initialize-config.test.ts	✅ Passed	149ms
tests/instance-isolation.test.ts	✅ Passed	147ms
tests/models-list.test.ts	✅ Passed	142ms
tests/responses-background-lifecycle.test.ts	✅ Passed	190ms
tests/responses-body-method-errors.test.ts	✅ Passed	305ms
tests/responses-cancel-timeout.test.ts	✅ Passed	192ms
tests/responses-cancel.test.ts	✅ Passed	266ms
tests/responses-compact-retries.test.ts	✅ Passed	230ms
tests/responses-compact.test.ts	✅ Passed	216ms
tests/responses-create-advanced-stream.test.ts	✅ Passed	118ms
tests/responses-create-advanced.test.ts	✅ Passed	200ms
tests/responses-create-disconnect.test.ts	✅ Passed	1.167s
tests/responses-create-errors.test.ts	✅ Passed	210ms
tests/responses-create-malformed-api-responses.test.ts	✅ Passed	188ms
tests/responses-create-retries.test.ts	✅ Passed	239ms
tests/responses-create-stream-failures.test.ts	✅ Passed	233ms
tests/responses-create-stream-timeout.test.ts	✅ Passed	2.177s
tests/responses-create-stream-wire.test.ts	✅ Passed	2.659s
tests/responses-create-stream.test.ts	✅ Passed	91ms
tests/responses-create-terminal-states.test.ts	✅ Passed	226ms
tests/responses-create-timeout.test.ts	✅ Passed	194ms
tests/responses-create.test.ts	✅ Passed	129ms
tests/responses-delete.test.ts	✅ Passed	131ms
tests/responses-input-items-errors.test.ts	✅ Passed	171ms
tests/responses-input-items-list.test.ts	✅ Passed	146ms
tests/responses-input-items-options.test.ts	✅ Passed	229ms
tests/responses-input-tokens-count-timeout.test.ts	✅ Passed	224ms
tests/responses-input-tokens-count.test.ts	✅ Passed	331ms
tests/responses-malformed-inputs.test.ts	✅ Passed	2.188s
tests/responses-not-found-errors.test.ts	✅ Passed	236ms
tests/responses-parse.test.ts	✅ Passed	174ms
tests/responses-retrieve-retries.test.ts	✅ Passed	263ms
tests/responses-retrieve.test.ts	✅ Passed	226ms
tests/responses-stored-method-errors.test.ts	✅ Passed	563ms
tests/retry-behavior.test.ts	✅ Passed	3.157s
tests/sdk-error-shape.test.ts	✅ Passed	278ms

View OkTest run #28826481734

_{SDK merge (69f06cc8d633) · head (39dc115421f3) · base (95b54e589491) · OkTest (7fc645091b1a)}