fix: allow claude backend to read env from setting.json while preventing recursion (#92)

* fix: allow claude backend to read env from setting.json while preventing recursion

Fixes #89

Problem:
- --setting-sources "" prevents claude from reading ~/.claude/setting.json env
- Removing it causes infinite recursion via skills/commands/agents loading

Solution:
- Keep --setting-sources "" to block all config sources
- Add loadMinimalEnvSettings() to extract only env from setting.json
- Pass env explicitly via --settings parameter
- Update tests to validate dynamic --settings parameter

Benefits:
- Claude backend can access ANTHROPIC_API_KEY and other env vars
- Skills/commands/agents remain blocked, preventing recursion
- Graceful degradation if setting.json doesn't exist

Generated with SWE-Agent.ai

Co-Authored-By: SWE-Agent.ai <noreply@swe-agent.ai>

* security: pass env via process environment instead of command line

Critical security fix for issue #89:
- Prevents ANTHROPIC_API_KEY leakage in process command line (ps)
- Prevents sensitive values from being logged in wrapper logs

Changes:
1. executor.go:
   - Add SetEnv() method to commandRunner interface
   - realCmd merges env with os.Environ() and sets to cmd.Env
   - All test mocks implement SetEnv()

2. backend.go:
   - Change loadMinimalEnvSettings() to return map[string]string
   - Use os.UserHomeDir() instead of os.Getenv("HOME")
   - Add 1MB file size limit check
   - Only accept string values in env (reject non-strings)
   - Remove --settings parameter (no longer in command line)

3. Tests:
   - Add loadMinimalEnvSettings() unit tests
   - Remove --settings validation (no longer in args)
   - All test mocks implement SetEnv()

Security improvements:
- No sensitive values in argv (safe from ps/logs)
- Type-safe env parsing (string-only)
- File size limit prevents memory issues
- Graceful degradation if setting.json missing

Tests: All pass (30.912s)

Generated with SWE-Agent.ai

Co-Authored-By: SWE-Agent.ai <noreply@swe-agent.ai>

---------

Co-authored-by: SWE-Agent.ai <noreply@swe-agent.ai>

codeagent-wrapper/backend.go

@@ -1,5 +1,11 @@
 package main
 
+import (
+	"encoding/json"
+	"os"
+	"path/filepath"
+)
+
 // Backend defines the contract for invoking different AI CLI backends.
 // Each backend is responsible for supplying the executable command and
 // building the argument list based on the wrapper config.
@@ -29,6 +35,51 @@ func (ClaudeBackend) BuildArgs(cfg *Config, targetArg string) []string {
 	return buildClaudeArgs(cfg, targetArg)
 }
 
+const maxClaudeSettingsBytes = 1 << 20 // 1MB
+
+// loadMinimalEnvSettings 从 ~/.claude/setting.json 只提取 env 配置。
+// 只接受字符串类型的值；文件缺失/解析失败/超限都返回空。
+func loadMinimalEnvSettings() map[string]string {
+	home, err := os.UserHomeDir()
+	if err != nil || home == "" {
+		return nil
+	}
+
+	settingPath := filepath.Join(home, ".claude", "setting.json")
+	info, err := os.Stat(settingPath)
+	if err != nil || info.Size() > maxClaudeSettingsBytes {
+		return nil
+	}
+
+	data, err := os.ReadFile(settingPath)
+	if err != nil {
+		return nil
+	}
+
+	var cfg struct {
+		Env map[string]any `json:"env"`
+	}
+	if err := json.Unmarshal(data, &cfg); err != nil {
+		return nil
+	}
+	if len(cfg.Env) == 0 {
+		return nil
+	}
+
+	env := make(map[string]string, len(cfg.Env))
+	for k, v := range cfg.Env {
+		s, ok := v.(string)
+		if !ok {
+			continue
+		}
+		env[k] = s
+	}
+	if len(env) == 0 {
+		return nil
+	}
+	return env
+}
+
 func buildClaudeArgs(cfg *Config, targetArg string) []string {
 	if cfg == nil {
 		return nil