fix: permission-prompt-tool response format and scaffold .claude/settings.json

- Return { behavior: "allow", updatedInput: <input> } from prompt_permission
  to match the Claude Code SDK expected format (was returning just
  { behavior: "allow" } which failed validation)
- Scaffold .claude/settings.json with sensible permission defaults (Edit,
  Write, common Bash commands, mcp__story-kit__*) so fresh projects don't
  trigger constant permission prompts

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

server/src/http/mcp.rs

@@ -1816,7 +1816,7 @@ async fn tool_prompt_permission(args: &Value, ctx: &AppContext) -> Result<String
         .send(crate::http::context::PermissionForward {
             request_id: request_id.clone(),
             tool_name: tool_name.clone(),
-            tool_input,
+            tool_input: tool_input.clone(),
             response_tx,
         })
         .map_err(|_| "No active WebSocket session to receive permission request".to_string())?;
@@ -1834,11 +1834,10 @@ async fn tool_prompt_permission(args: &Value, ctx: &AppContext) -> Result<String
     .map_err(|_| "Permission response channel closed unexpectedly".to_string())?;
 
     if approved {
-        // Claude Code SDK validates the response as a union:
-        //   { behavior: "allow" } | { behavior: "deny", message: string }
-        // Previously we returned {"updatedInput": ...} which didn't match
-        // either variant, causing intermittent `invalid_union` errors.
-        Ok(json!({"behavior": "allow"}).to_string())
+        // Claude Code SDK expects:
+        //   Allow:  { behavior: "allow", updatedInput: <record> }
+        //   Deny:   { behavior: "deny", message: string }
+        Ok(json!({"behavior": "allow", "updatedInput": tool_input}).to_string())
     } else {
         slog_warn!("[permission] User denied permission for '{tool_name}'");
         Ok(json!({
@@ -3374,7 +3373,7 @@ stage = "coder"
     }
 
     #[tokio::test]
-    async fn tool_prompt_permission_approved_returns_allow_behavior() {
+    async fn tool_prompt_permission_approved_returns_updated_input() {
         let tmp = tempfile::tempdir().unwrap();
         let ctx = test_ctx(tmp.path());
 
@@ -3397,7 +3396,11 @@ stage = "coder"
         let parsed: Value = serde_json::from_str(&result).expect("result should be valid JSON");
         assert_eq!(
             parsed["behavior"], "allow",
-            "approved must return behavior:allow for Claude Code SDK compatibility"
+            "approved must return behavior:allow"
+        );
+        assert_eq!(
+            parsed["updatedInput"]["command"], "echo hello",
+            "approved must return updatedInput with original tool input for Claude Code SDK compatibility"
         );
     }