CREATIVE WORKFLOW:
                              1. Upload the image/GIF via `upload_image_creative` → response gives `id` (the imageLibraryId).
                              2. Pass that integer as `creativeID` here.
                              - Need a new image? `generate_brand_creative` → `upload_image_creative` → `create_update_image_ad`.

                            ALSO KNOWN AS: create image ad, update image ad, edit image ad,
                            modify image ad, image creative, post image, image post, photo ad.

                            KEYWORDS: image, gif, create, update, edit, modify, ad, ads, image ad, image ads,
                            image creative, photo, picture, banner, image campaign, image upload,
                            LinkedIn image, Facebook image, Instagram image, Reddit image, IG post.

                            CLIENT-SIDE VALIDATION (refuses what the platform UI would also reject):
                              - adName: required, max 50 chars, pattern `[a-zA-Z0-9 _.?,:'/+\-=&;%$#\[\]|()]`.
                              - creativeID: required integer (imageLibraryId from `upload_image_creative`).
                              - Landing-page URL is per channel (`facebookDisplayURL`,
                                `instagramDisplayURL`, `linkedinDisplayURL`, `redditDisplayURL`).
                                Required for FB/IG/LinkedIn, optional for Reddit. Per-channel
                                caps: LinkedIn max 2000, Reddit max 100, FB/IG no length rule.
                                URL format accepts both `metadata.io` and `https://metadata.io`
                                for IMAGE ads. If only one channel's URL is set the server fans
                                it across the other targeted channels; each channel's cap is
                                then enforced per channel.
                              - LinkedIn: linkedinText (required, max 3000), linkedinHeadline (required,
                                max 200), linkedinDescription (optional, max 300 — IMAGE only),
                                linkedinCTA (required, must be a valid LinkedIn CTA enum).
                              - Facebook: metaCTA (required), facebookText (required, no length rule on
                                Facebook), facebookHeadline (required, max 250), facebookDescription
                                (optional, max 300).
                              - Instagram: metaCTA (required), instagramText (required, max 125),
                                instagramHeadline (required, max 40), instagramDescription (optional, max 30).
                              - FB+IG ad with one body text: set just one of facebookText / instagramText
                                and the server copies it across (capped at the receiving channel's limit).
                                Set both explicitly only when you want per-channel copy.
                              - Reddit: redditHeadline (required, max 300), redditCTA (required, must be a
                                valid Reddit CTA enum). redditThumbnailLibraryId is optional and defaults to
                                creativeID.

                            COMMON CTA VALUES:
                              - LinkedIn: LEARN_MORE, REGISTER, APPLY_NOW, DOWNLOAD, JOIN, SIGN_UP,
                                GET_QUOTE, ATTEND, REQUEST_DEMO, SUBSCRIBE. (UNLOCK_FULL_DOCUMENT is
                                DOCUMENT-only — use create_update_document_ad, not this tool.)
                              - Facebook/Instagram: APPLY_NOW, DOWNLOAD, GET_QUOTE, LEARN_MORE, SIGN_UP, SUBSCRIBE.
                                (SCREAMING_SNAKE form only; the platform supports a strict subset of Meta's
                                native catalog. Out-of-set values like BOOK_NOW / GET_STARTED are rejected.)
                              - Reddit: Apply Now, Contact Us, Download, Get a Quote, Learn More, Play Now,
                                Sign Up, View More, Watch Now, Book Now, Listen Now, Read More, Subscribe.

                            See `create_update_video_ad` for video-creative ads (different libraryId source +
                            stricter URL format).