#7502: feat(whatsapp): send WebP files as stickers

## Summary Send WebP files as WhatsApp stickers instead of image attachments. Currently, there is no way to send stickers via the WhatsApp plugin — all WebP files are converted to JPEG and sent as regular images. This PR adds automatic sticker detection for WebP files. ## Why Many bots and agents need to send stickers as part of natural WhatsApp conversations. Stickers are a core part of WhatsApp communication — they're used constantly in both DMs and group chats. Without sticker support, bots feel less natural and miss out on a major way humans communicate on the platform. Use cases: - Bots that react with stickers (memes, emoji stickers, custom packs) - Agents that can receive stickers from users and send them back - Fun/social bots that participate naturally in group chats - Forwarding stickers between chats or users Currently, `message action=sticker` returns `"not supported for channel whatsapp"`, and sending a `.webp` file delivers it as a regular image. This means there's zero sticker send capability on WhatsApp today. ## Changes **`src/web/media.ts`** - Preserve WebP files under 500KB (skip JPEG optimization) so the original format reaches the send layer - Without this, WebP → JPEG conversion happens before the send function ever sees the file **`src/web/inbound/send-api.ts`** - Route WebP buffers through Baileys' `{ sticker: buffer }` message type instead of `{ image: buffer }` - Detection: `image/webp` + under 500KB + no caption = sticker ## How to send a sticker Send a `.webp` file with no caption (or empty caption) via the message tool: ``` message action=send channel=whatsapp target=<jid> message="." filePath=/path/to/sticker.webp ``` WhatsApp sticker requirements: - Format: WebP - Size: under 500KB - Recommended dimensions: 512x512px If a caption is provided, the WebP is sent as a normal image (existing behavior preserved). ## Testing Tested locally with Baileys on WhatsApp. Confirmed: - ✅ WebP files sent as proper stickers (not image attachments) - ✅ WebP files with captions still sent as regular images - ✅ Non-WebP images unaffected - ✅ Existing GIF/video/audio/document paths unaffected - ✅ Inbound sticker reception already works (no changes needed) ## Future improvements A dedicated `asSticker` flag in send options would be more explicit than relying on empty caption detection. This PR takes the simpler auto-detect approach as a first step. A follow-up could also add `action=sticker` support to the message tool for WhatsApp. Closes #7476 <!-- greptile_comment --> <h2>Greptile Overview</h2> <h3>Greptile Summary</h3> This PR adds automatic WebP→sticker routing for WhatsApp outbound sends: `src/web/media.ts` preserves small WebP images (<=500KB) by skipping JPEG optimization so the original WebP reaches the sender, and `src/web/inbound/send-api.ts` sends qualifying WebP buffers via Baileys’ `{ sticker: buffer }` message type when there’s no caption. The approach integrates cleanly with the existing `loadWebMedia()` → `active.sendMessage()` pipeline and keeps other media types (image/audio/video/document) unchanged. <h3>Confidence Score: 4/5</h3> - This PR looks safe to merge with low functional risk; the main concerns are maintainability/contract clarity rather than immediate breakage. - Core logic is small and localized, and the WebP sticker routing is guarded by mimetype/size/empty-caption checks. I didn’t find clear runtime-breaking changes in existing call paths (current callers pass `text` as a string). Remaining issues are duplicated thresholds and a slight type/contract mismatch that could become a future footgun. - src/web/inbound/send-api.ts (caption contract + duplicated threshold), src/web/media.ts (duplicated threshold/error labeling). <!-- greptile_other_comments_section --> _{(4/5) You can add custom instructions or style guidelines for the agent [here](https://app.greptile.com/review/github)!} **Context used:** - Context from `dashboard` - CLAUDE.md ([source](https://app.greptile.com/review/custom-context?memory=fd949e91-5c3a-4ab5-90a1-cbe184fd6ce8)) - Context from `dashboard` - AGENTS.md ([source](https://app.greptile.com/review/custom-context?memory=0d0c8278-ef8e-4d6c-ab21-f5527e322f13)) <!-- /greptile_comment -->