feat: add Telegram file attachment support (inbound + outbound)

Inbound:
- tg-ingest detects document/photo/audio/video/voice attachments
- Downloads files via Telegram Bot API (getFile + download)
- Inlines small text files (<50KB) directly in the prompt
- Stores binary/large files to S3 (attachments/{chat_id}/{update_id}/{filename})
- agent-runner appends file context to the AgentCore prompt

Outbound:
- New send_file tool for the agent to send documents back to users
- TelegramAdapter.send_document uses multipart/form-data POST
- CDK grants tg-ingest S3 write access and passes bucket name env var

src/lambdas/agent-runner/handler.py

@@ -184,6 +184,18 @@ def handler(event, context):
         ]
         prompt = f"You have {len(records)} queued messages:\n" + "\n".join(lines)
 
+    # ── Attach file context if present ────────────────────────────────────
+    attachment = first.get('attachment')
+    if attachment:
+        file_name = attachment.get('file_name', 'unknown')
+        if 'inline_content' in attachment:
+            prompt += f"\n\n[Attached file: {file_name}]\n```\n{attachment['inline_content']}\n```"
+        elif 's3_key' in attachment:
+            s3_ref = f"s3://{attachment['s3_bucket']}/{attachment['s3_key']}"
+            prompt += f"\n\n[Attached file: {file_name} ({attachment.get('mime_type', '')}) — stored at {s3_ref}]"
+        elif 'error' in attachment:
+            prompt += f"\n\n[Attachment {file_name} could not be processed: {attachment['error']}]"
+
     # ── Build payload for AgentCore Runtime 1 ────────────────────────────
     payload: dict[str, Any] = {
         'prompt': prompt,