update_brand_kit

Update existing brand kit with brand DNA parameters. Only company_url is required; all others are optional.

                    UPDATABLE FIELDS (grouped by section):

                    TOP-LEVEL:
                    - long_description: Company marketing description
                    - logo_url: Direct URL to logo image
                    - search_keywords: List of SEO/search keywords
                    - colors: Legacy flat color list [{hex, type, name?}]
                    - fonts: Legacy flat font list [{name, type}]
                    - website_background: Hex color of the brand website's background, used by generate_brand_creative as the default ad background

                    COLOR PALETTES (each entry: {hex, name, usage}):
                    - primary_colors, accent_colors, extended_palette, semantic_colors

                    TYPOGRAPHY (string values):
                    - primary_font, primary_font_usage, secondary_font, secondary_font_usage
                    - headline_font, headline_weight, headline_size, headline_case, headline_linespace, headline_letterspace
                    - eyebrow_font, eyebrow_weight, eyebrow_case, eyebrow_linespace, eyebrow_letterspace
                    - subtitle_font, subtitle_weight, subtitle_linespace, subtitle_letterspace
                    - body_font, body_weight, body_size, body_linespace, body_letterspace
                    - cta_font, cta_weight, cta_size, cta_linespace, cta_letterspace

                    LOGO USAGE:
                    - logo_on_dark, logo_on_light, logo_clear_space: string rules
                    - logo_misuse: list of misuse rules

                    CTA SYSTEM:
                    - button_shape, button_background, button_text_color, button_text_weight, button_text_case, button_padding
                    - standard_ctas: list of CTA labels
                    - cta_placement: placement guidance

                    SIGNATURE ELEMENTS:
                    - tagline, tagline_placement: strings
                    - tagline_variants, visual_motifs, promotional_elements: lists

                    MESSAGING:
                    - tone: string
                    - value_propositions, headline_formulas, proof_points: lists
                    - product_names: dict (e.g. {platform: "X", vlm: "Y"})

                    CONTENT HIERARCHY:
                    - content_hierarchy_order: list, content_hierarchy_spacing: string, content_hierarchy_text_max_width: string

                    PHOTOGRAPHY:
                    - photography_style, photography_treatment, photography_avoid: strings
                    - photography_subjects: list

                    RULES:
                    - dos: list of "do" rules
                    - donts: list of "don't" rules

                    LAYOUT & CHANNELS:
                    - primary_layouts: list of layout dicts
                    - channel_linkedin, channel_facebook, channel_display: channel config dicts

                    EXAMPLE: {"company_url": "ambient.ai", "tagline": "See what matters.", "headline_font": "Chakra Petch", "primary_colors": [{"hex": "#FFFFFF", "name": "White", "usage": "Primary background"}]}