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/executor_concurrent_test.go

@@ -87,6 +87,7 @@ type execFakeRunner struct {
 	process         processHandle
 	stdin           io.WriteCloser
 	dir             string
+	env             map[string]string
 	waitErr         error
 	waitDelay       time.Duration
 	startErr        error
@@ -129,6 +130,17 @@ func (f *execFakeRunner) StdinPipe() (io.WriteCloser, error) {
 }
 func (f *execFakeRunner) SetStderr(io.Writer) {}
 func (f *execFakeRunner) SetDir(dir string)   { f.dir = dir }
+func (f *execFakeRunner) SetEnv(env map[string]string) {
+	if len(env) == 0 {
+		return
+	}
+	if f.env == nil {
+		f.env = make(map[string]string, len(env))
+	}
+	for k, v := range env {
+		f.env[k] = v
+	}
+}
 func (f *execFakeRunner) Process() processHandle {
 	if f.process != nil {
 		return f.process