WSDL gap

Issue #239 optional-field audit confirms adgroups add/update only expose the common TEXT_AD_GROUP, DYNAMIC_TEXT_AD_GROUP, and SMART_AD_GROUP subtype paths. Cached WSDL also declares optional subtype blocks such as MobileAppAdGroup, DynamicTextFeedAdGroup, CpmBannerKeywordsAdGroup, CpmBannerUserProfileAdGroup, CpmVideoAdGroup, UnifiedAdGroup, and TextAdGroupFeedParams.

Expected CLI contract

• Audit each WSDL-declared ad group subtype and decide the PR split.
• Add typed --type values and explicit flags for supported subtype fields.
• Preserve per-type incompatible-flag rejection so unused subtype flags cannot be silently dropped.
• Keep canonical CLI syntax typed and single-line; no --json.
• Add dry-run tests and WSDL/audit coverage for each subtype added.

Verification

• direct adgroups add --type MOBILE_APP_AD_GROUP ... --dry-run
• direct adgroups update --id 1 --type DYNAMIC_TEXT_FEED_AD_GROUP ... --dry-run

Refs: #239.