fix(API): improve get /formats documentation

[Stephen Lumenta (sbl)]

Improves the documentation for get /formats: sharper descriptions, parameter docs, error responses, and usage examples.

Drafted with AI assistance and grounded in the API implementation. Please review for technical accuracy before merging; nothing is merged automatically.

Graded at 4.33/5 after this fix. Remaining open items (if any) are noted in the linked DEVEX issue.

🤖 Generated with Claude Code

[github-actions]

API changelog (oasdiff)

Doc-only edits (descriptions, examples) do not appear here.

10 changes: 0 error, 0 warning, 10 info
info	[response-property-became-required] at doc/compiled.json
	in API GET /formats
		the response property `items/api_name` became required for the status `200`

info	[response-property-became-required] at doc/compiled.json
	in API GET /formats
		the response property `items/default_encoding` became required for the status `200`

info	[response-property-became-required] at doc/compiled.json
	in API GET /formats
		the response property `items/default_file` became required for the status `200`

info	[response-property-became-required] at doc/compiled.json
	in API GET /formats
		the response property `items/description` became required for the status `200`

info	[response-property-became-required] at doc/compiled.json
	in API GET /formats
		the response property `items/exportable` became required for the status `200`

info	[response-property-became-required] at doc/compiled.json
	in API GET /formats
		the response property `items/extension` became required for the status `200`

info	[response-property-became-required] at doc/compiled.json
	in API GET /formats
		the response property `items/importable` became required for the status `200`

info	[response-property-became-required] at doc/compiled.json
	in API GET /formats
		the response property `items/includes_locale_information` became required for the status `200`

info	[response-property-became-required] at doc/compiled.json
	in API GET /formats
		the response property `items/name` became required for the status `200`

info	[response-property-became-required] at doc/compiled.json
	in API GET /formats
		the response property `items/renders_default_locale` became required for the status `200`