Fix Package Docs

Systematically find and fix all actionable API documentation issues in a Kibana plugin or package using check_package_docs.

Non-negotiable conventions

Only add JSDoc to exported public API — skip internal helpers that happen to be exported.
Never change runtime behavior — documentation edits only (no logic, type, or signature changes).
Use /** ... */ style (not //). Single-line /** Description. */ for simple items; multi-line for complex ones.
Descriptions are sentences: start with a capital letter, end with a period.
@param name - Description. (hyphen separator, not colon). Match every parameter in the signature.
Destructured object parameters: document nested properties with dot-notation tags (e.g., @param options.foo - Description.). The tooling supports arbitrary nesting (e.g., @param fns.fn1.foo.param). Each level must have its own @param tag.
@returns for non-void functions: always present; omit only for void/Promise<void>.
Use {@link OtherType} for cross-references to other Kibana types.
missingExports items need human judgment to decide whether to export — skip them and note in PR.