Renders a unified "Ask" or "Display" action button for chat-adjacent surfaces (source chips, inline cards, search result rows), replacing three divergent implementations with a single density-aware primitive. ## Key Components ### Types - **`SourceActionDensity`** — Union type `'inline' | 'card' | 'list-row'` controlling visual layout variant - **`SourceActionButtonProps`** — Component props including `chatRef`, `onDiscuss`, `density`, `label`, and `className` ### Constants - **`DENSITY_STYLES`** — Static map from `SourceActionDensity` to per-variant sizing, icon dimensions, label visibility, and Tailwind class strings. Adding a new surface requires only a new entry here. ### Component - **`SourceActionButton`** — Returns `null` when `chatRef` or `onDiscuss` is absent (safe to render unconditionally). Selects `MessageSquare` or `FileText` icon based on whether `label` is `'Display'`. Delegates to the UI-Kit `` for consistent DOM structure and accessibility. ## Usage Example ```typescript import { SourceActionButton } from './source-action-button' import type { ChatRef } from './chat-ref.types' const ref: ChatRef = { id: 'doc-42', title: 'Q4 Report' } // Compact icon-only button beside a source chip openChat(r)} density="inline" /> // Labelled button inside an inline card openChat(r)} density="card" label="Ask" /> // Labelled button with display semantics in a list row openViewer(r)} density="list-row" label="Display" /> ``` **Visibility rules:** the component renders `null` (no DOM node) when either `chatRef` or `onDiscuss` is `undefined`/`null`, so call sites need no conditional wrapping.