Update external-v3.yaml to latest Ads API spec and align skills

[amurph491]

Spec changes:

• Add new endpoints: business/ad account members, invitations, aggregated totals reporting
• Add new schemas: catalog ads, signal events, business roles, SKAdEnabled, cookie opt-in, asset metadata
• Add AUTOBID bid strategy, CATALOG asset format, and new campaign objectives (PODCAST_STREAMS, APP_INSTALLS, WEBSITE_VISITS)
• Add new insight dimensions: CITY, METRO, PLACEMENT, PODCAST_EPISODE_TOPIC, REGION
• Add insight_dimension parameter to async report creation
• Add OpenAPI links to campaign creation response chaining
• Restructure vendor extensions into typed objects (x-spotify-common-mistakes, x-spotify-requires, x-spotify-flow-output, x-spotify-defaults, x-spotify-enum-descriptions)
• Remove deprecated schemas (AdAccountInternalRequestEntity, SurveyQuestionText, UpdateSurveyQuestionRequest)
• Remove updateSurveyQuestion endpoint
• Update lookback_days max from 30 to 180

Skill alignment:

• Add AUTOBID, CATALOG, new objectives across all operational skills
• Update insight dimensions in report skill and api-reference
• Add aggregated totals endpoint to report skill
• Remove restricted_ad_category from campaign schemas
• Clean up internal-only references from enums

Description

Checklist

• Tested against the Spotify Ads API with Codex or Claude Code
• Existing skills still work as expected
• SKILL.md frontmatter is valid (name, description, allowed-tools)
• README or CHANGELOG updated (if user-facing change)
• Curl commands follow API conventions documented in AGENTS.md