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_test.go

@@ -1,7 +1,9 @@
 package main
 
 import (
+	"bytes"
 	"os"
+	"path/filepath"
 	"reflect"
 	"testing"
 )
@@ -148,3 +150,64 @@ func TestClaudeBuildArgs_BackendMetadata(t *testing.T) {
 		}
 	}
 }
+
+func TestLoadMinimalEnvSettings(t *testing.T) {
+	home := t.TempDir()
+	t.Setenv("HOME", home)
+	t.Setenv("USERPROFILE", home)
+
+	t.Run("missing file returns empty", func(t *testing.T) {
+		if got := loadMinimalEnvSettings(); len(got) != 0 {
+			t.Fatalf("got %v, want empty", got)
+		}
+	})
+
+	t.Run("valid env returns string map", func(t *testing.T) {
+		dir := filepath.Join(home, ".claude")
+		if err := os.MkdirAll(dir, 0o755); err != nil {
+			t.Fatalf("MkdirAll: %v", err)
+		}
+		path := filepath.Join(dir, "setting.json")
+		data := []byte(`{"env":{"ANTHROPIC_API_KEY":"secret","FOO":"bar"}}`)
+		if err := os.WriteFile(path, data, 0o600); err != nil {
+			t.Fatalf("WriteFile: %v", err)
+		}
+
+		got := loadMinimalEnvSettings()
+		if got["ANTHROPIC_API_KEY"] != "secret" || got["FOO"] != "bar" {
+			t.Fatalf("got %v, want keys present", got)
+		}
+	})
+
+	t.Run("non-string values are ignored", func(t *testing.T) {
+		dir := filepath.Join(home, ".claude")
+		path := filepath.Join(dir, "setting.json")
+		data := []byte(`{"env":{"GOOD":"ok","BAD":123,"ALSO_BAD":true}}`)
+		if err := os.WriteFile(path, data, 0o600); err != nil {
+			t.Fatalf("WriteFile: %v", err)
+		}
+
+		got := loadMinimalEnvSettings()
+		if got["GOOD"] != "ok" {
+			t.Fatalf("got %v, want GOOD=ok", got)
+		}
+		if _, ok := got["BAD"]; ok {
+			t.Fatalf("got %v, want BAD omitted", got)
+		}
+		if _, ok := got["ALSO_BAD"]; ok {
+			t.Fatalf("got %v, want ALSO_BAD omitted", got)
+		}
+	})
+
+	t.Run("oversized file returns empty", func(t *testing.T) {
+		dir := filepath.Join(home, ".claude")
+		path := filepath.Join(dir, "setting.json")
+		data := bytes.Repeat([]byte("a"), maxClaudeSettingsBytes+1)
+		if err := os.WriteFile(path, data, 0o600); err != nil {
+			t.Fatalf("WriteFile: %v", err)
+		}
+		if got := loadMinimalEnvSettings(); len(got) != 0 {
+			t.Fatalf("got %v, want empty", got)
+		}
+	})
+}