Remove legacy claude field and working_dir backward compat

- Remove Claude field alias from Task struct (already removed in sandbox)
- Remove UnmarshalJSON from AgentConfig that silently accepted working_dir
- Remove legacy claude fallback in scanTask (db.go)
- Remove TestGetTask_BackwardCompatibility test that validated removed behavior

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

1 files changed, 0 insertions, 19 deletions

diff --git a/internal/task/task.go b/internal/task/task.go
index 4977f40..c0aa036 100644
--- a/internal/task/task.go
+++ b/internal/task/task.go
@@ -1,7 +1,6 @@
 package task
 
 import (
-	"encoding/json"
 	"time"
 )
 
@@ -43,24 +42,6 @@ type AgentConfig struct {
 	SkipPlanning       bool     `yaml:"skip_planning"       json:"skip_planning"`
 }
 
-// UnmarshalJSON reads project_dir with fallback to legacy working_dir.
-func (c *AgentConfig) UnmarshalJSON(data []byte) error {
-	type Alias AgentConfig
-	aux := &struct {
-		ProjectDir string `json:"project_dir"`
-		WorkingDir string `json:"working_dir"` // legacy
-		*Alias
-	}{Alias: (*Alias)(c)}
-	if err := json.Unmarshal(data, aux); err != nil {
-		return err
-	}
-	if aux.ProjectDir != "" {
-		c.ProjectDir = aux.ProjectDir
-	} else {
-		c.ProjectDir = aux.WorkingDir
-	}
-	return nil
-}
 
 type RetryConfig struct {
 	MaxAttempts int    `yaml:"max_attempts" json:"max_attempts"`