feat(telegram): add sticker support with vision caching

Add support for receiving and sending Telegram stickers:

Inbound:
- Receive static WEBP stickers (skip animated/video)
- Process stickers through dedicated vision call for descriptions
- Cache vision descriptions to avoid repeated API calls
- Graceful error handling for fetch failures

Outbound:
- Add sticker action to send stickers by fileId
- Add sticker-search action to find cached stickers by query
- Accept stickerId from shared schema, convert to fileId

Cache:
- Store sticker metadata (fileId, emoji, setName, description)
- Fuzzy search by description, emoji, and set name
- Persist to ~/.clawdbot/telegram/sticker-cache.json

Config:
- Single `channels.telegram.actions.sticker` option enables both
  send and search actions

🤖 AI-assisted: Built with Claude Code (claude-opus-4-5)
Testing: Fully tested - unit tests pass, live tested on dev gateway
The contributor understands and has reviewed all code changes.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/telegram/bot-handlers.ts

@@ -112,11 +112,19 @@ export const registerTelegramHandlers = ({
       const captionMsg = entry.messages.find((m) => m.msg.caption || m.msg.text);
       const primaryEntry = captionMsg ?? entry.messages[0];
 
-      const allMedia: Array<{ path: string; contentType?: string }> = [];
+      const allMedia: Array<{
+        path: string;
+        contentType?: string;
+        stickerMetadata?: { emoji?: string; setName?: string; fileId?: string };
+      }> = [];
       for (const { ctx } of entry.messages) {
         const media = await resolveMedia(ctx, mediaMaxBytes, opts.token, opts.proxyFetch);
         if (media) {
-          allMedia.push({ path: media.path, contentType: media.contentType });
+          allMedia.push({
+            path: media.path,
+            contentType: media.contentType,
+            stickerMetadata: media.stickerMetadata,
+          });
         }
       }
 
@@ -595,7 +603,24 @@ export const registerTelegramHandlers = ({
         }
         throw mediaErr;
       }
-      const allMedia = media ? [{ path: media.path, contentType: media.contentType }] : [];
+
+      // Skip sticker-only messages where the sticker was skipped (animated/video)
+      // These have no media and no text content to process.
+      const hasText = Boolean((msg.text ?? msg.caption ?? "").trim());
+      if (msg.sticker && !media && !hasText) {
+        logVerbose("telegram: skipping sticker-only message (unsupported sticker type)");
+        return;
+      }
+
+      const allMedia = media
+        ? [
+            {
+              path: media.path,
+              contentType: media.contentType,
+              stickerMetadata: media.stickerMetadata,
+            },
+          ]
+        : [];
       const senderId = msg.from?.id ? String(msg.from.id) : "";
       const conversationKey =
         resolvedThreadId != null ? `${chatId}:topic:${resolvedThreadId}` : String(chatId);