feat: handle market challenges natively without LLM

Add Type/MarketEndpoint/AnswerFormat fields to Challenge struct.
When challenge.Type == "market", bypass LLM and HTTP GET the
market_endpoint to fetch the live count (total field), returning
the integer as the answer directly.

This covers the new 20% market challenge rate introduced in the
inscribe-worker without burning LLM calls on deterministic answers.

Author: clawplaza

internal/api/types.go

@@ -98,6 +98,12 @@ type Challenge struct {
 	ID        string `json:"id"`
 	Prompt    string `json:"prompt"`
 	ExpiresIn int    `json:"expires_in"`
+
+	// Market challenge fields (Type == "market").
+	// The CLI should HTTP GET MarketEndpoint (no auth) and return the count as the answer.
+	Type           string `json:"type,omitempty"`             // "market" | "" (language challenge)
+	MarketEndpoint string `json:"market_endpoint,omitempty"` // read-only API URL
+	AnswerFormat   string `json:"answer_format,omitempty"`   // "integer"
 }
 
 // GenesisNFT represents an agent's won NFT.

internal/miner/loop.go

@@ -2,10 +2,13 @@ package miner
 
 import (
 	"context"
+	"encoding/json"
 	"errors"
 	"fmt"
+	"io"
 	"log/slog"
 	"math/rand"
+	"net/http"
 	"strconv"
 	"strings"
 	"time"
@@ -485,7 +488,45 @@ func (m *Miner) mineOnce(ctx context.Context) (*api.InscribeResponse, error) {
 	return resp, nil
 }
 
+func (m *Miner) answerMarketChallenge(ctx context.Context, challenge *api.Challenge) (string, error) {
+	slog.Info("Market challenge: fetching live data", "endpoint", challenge.MarketEndpoint)
+	fmt.Printf(i18n.Tr("  [Market] Fetching: %s\n", "  [市场] 获取数据: %s\n"), challenge.MarketEndpoint)
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, challenge.MarketEndpoint, nil)
+	if err != nil {
+		return "", fmt.Errorf("market challenge: build request: %w", err)
+	}
+
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return "", fmt.Errorf("market challenge: http get: %w", err)
+	}
+	defer resp.Body.Close()
+
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return "", fmt.Errorf("market challenge: read body: %w", err)
+	}
+
+	var result struct {
+		Total int `json:"total"`
+	}
+	if err := json.Unmarshal(body, &result); err != nil {
+		return "", fmt.Errorf("market challenge: parse response: %w", err)
+	}
+
+	answer := strconv.Itoa(result.Total)
+	slog.Info("Market challenge answered", "total", result.Total)
+	fmt.Printf(i18n.Tr("  [Market] Answer: %s\n", "  [市场] 答案: %s\n"), answer)
+	return answer, nil
+}
+
 func (m *Miner) answerChallenge(ctx context.Context, challenge *api.Challenge) (string, error) {
+	// Market challenges bypass LLM — fetch live data from the provided endpoint.
+	if challenge.Type == "market" && challenge.MarketEndpoint != "" {
+		return m.answerMarketChallenge(ctx, challenge)
+	}
+
 	DisplayChallenge(challenge.Prompt)
 	display := challenge.Prompt
 	if len(display) > 80 {