Add doc.go with package-level godoc for all 15 packages, runnable
example functions for chat completion, streaming, embeddings, and
error handling, plus build-tagged integration tests for live API
validation.
Agents lifecycle: create, get, list, update, delete, version switching,
version listing, aliases (set/list/delete). Agent types include tools
(function, web_search, code_interpreter, etc.), guardrails, completion
args. Moderation: text + chat endpoints with categories and scores.
Classification: text + chat endpoints with target result scores.
