fix: validate complete output format names

[Shubham-Padkonde]

format() currently accepts unsupported values such as jsonn, not-json, and iso19116 because re.search finds a valid substring. These values then become invalid endpoint extensions instead of raising the documented ValueError locally.

Match the entire format name and allow multi-digit UMM version components, preserving valid values such as umm_json_v1_18. Fix missing commas in four existing valid-format fixtures, which had silently concatenated two UMM version strings.

Validation: all 152 tests pass. Twenty invalid-format cases across five query types fail before the fix; three cases verify valid UMM versions. git diff --check passes. This branch is based directly on develop and does not include the separate UMM result-parsing change.