refactor(app_controller): migrate 5 callback sites to Result (batch 1)

Migrated 5 INTERNAL_BROAD_CATCH sites to the data-oriented Result[T] pattern:

1. _handle_custom_callback (L537)
   - Narrowed: except Exception -> except (TypeError, ValueError, AttributeError, KeyError, IndexError, RuntimeError, OSError)
   - Returns Result[None] via OK on success, Result(data=None, errors=[...]) on failure
   - logging.debug added per Heuristic #19

2. _handle_click (L579)
   - Narrowed: except Exception -> except (TypeError, ValueError, AttributeError, KeyError, IndexError, RuntimeError)
   - Preserves the no-arg fallback (func()) behavior
   - Returns Result[None] on success/failure

3. cb_load_prior_log inner (L2046) - bare except in json.dumps
   - Narrowed: bare except -> except (TypeError, ValueError)
   - Added logging.debug for tool_calls serialization failure
   - Preserves the [TOOL CALLS PRESENT] fallback

4. cb_load_prior_log inner (L2068) - bare except in datetime parsing
   - Narrowed: bare except -> except (ValueError, TypeError, KeyError, IndexError)
   - Added logging.debug for first_ts parse failure
   - Preserves the time.time() fallback

5. cb_load_prior_log outer (L2081) - except Exception
   - Narrowed: except Exception -> except (OSError, IOError, json.JSONDecodeError, ValueError, TypeError, KeyError, AttributeError)
   - Returns Result[None] with ErrorInfo; preserves the ai_status set + early return
   - State mutations after the try block are still skipped on error (same as before)

Test impact: 5 new test_app_controller_result tests verify the contract.
tier-1-unit-core: 885 passed (was 883, +2 from earlier Phase 1); 1 expected
failure (test_app_controller_does_not_use_broad_except) will pass after
all 32 sites are migrated across Phases 2-4.

Refs: spec.md FR1, plan.md Task 2.2
Refs: 26e57577 (Phase 1 regression fix on the same file)

scripts/tier2/artifacts/result_migration_app_controller_20260618/inspect_sites.py

@@ -0,0 +1,16 @@
+import json
+import subprocess
+r = subprocess.run(['uv', 'run', 'python', 'scripts/audit_exception_handling.py', '--json'], capture_output=True, text=True)
+data = json.loads(r.stdout)
+app = [f for f in data['files'] if 'app_controller' in f.get('filename', '')][0]
+findings = app['findings']
+broad = [f for f in findings if f.get('category') == 'INTERNAL_BROAD_CATCH']
+# Batch 1: L539, L581, L2048, L2070, L2083
+for line_num in [539, 581, 2048, 2070, 2083]:
+    matches = [f for f in broad if f.get('line') == line_num]
+    if matches:
+        f = matches[0]
+        ctx = f.get('context', '')
+        print(f'=== L{line_num} (category: {f.get("category", "")}, kind: {f.get("kind", "")}) ===')
+        print(f'  context: {ctx[:300]}')
+        print()

src/app_controller.py

@@ -38,7 +38,7 @@ from src import shell_runner
 from src import theme_2 as theme
 from src import thinking_parser
 from src import tool_presets
-from src.result_types    import Result, ErrorInfo, ErrorKind
+from src.result_types    import Result, ErrorInfo, ErrorKind, OK
 
 from src.context_presets import ContextPresetManager
 from src.file_cache      import ASTParser
@@ -529,17 +529,24 @@ def _handle_show_track_proposal(controller: 'AppController', task: dict):
  controller.proposed_tracks = task.get("payload", [])
  controller._show_track_proposal_modal = True
 
-def _handle_custom_callback(controller: 'AppController', task: dict):
+def _handle_custom_callback(controller: 'AppController', task: dict) -> Result[None]:
  """[SDM: AppController._handle_custom_callback]"""
  cb = task.get("callback")
  args = task.get("args", [])
  if callable(cb):
   try:
    cb(*args)
-  except Exception as e:
-   print(f"Error in direct custom callback: {e}")
+  except (TypeError, ValueError, AttributeError, KeyError, IndexError, RuntimeError, OSError) as e:
+   logging.getLogger(__name__).debug("custom callback error: %s", e, extra={"source": "app_controller._handle_custom_callback"})
+   return Result(data=None, errors=[ErrorInfo(
+    kind=ErrorKind.INTERNAL,
+    message=str(e),
+    source="app_controller._handle_custom_callback",
+    original=e,
+   )])
  elif cb in controller._predefined_callbacks:
   controller._predefined_callbacks[cb](*args)
+ return OK
 
 def _handle_set_value(controller: 'AppController', task: dict):
  """[SDM: AppController._handle_set_value]"""
@@ -562,7 +569,7 @@ def _handle_set_value(controller: 'AppController', task: dict):
     new_dict = {**current, key: value}
     setattr(controller, attr_name, new_dict)
 
-def _handle_click(controller: 'AppController', task: dict):
+def _handle_click(controller: 'AppController', task: dict) -> Result[None]:
  """[SDM: AppController._handle_click]"""
  item = task.get("item")
  user_data = task.get("user_data")
@@ -578,8 +585,19 @@ def _handle_click(controller: 'AppController', task: dict):
     func(user_data=user_data)
    else:
     func()
-  except Exception:
-   func()
+   return OK
+  except (TypeError, ValueError, AttributeError, KeyError, IndexError, RuntimeError) as e:
+   logging.getLogger(__name__).debug("click handler error, trying no-arg fallback: %s", e, extra={"source": "app_controller._handle_click"})
+   try:
+    func()
+   except (TypeError, ValueError, AttributeError, KeyError, IndexError, RuntimeError) as e2:
+    return Result(data=None, errors=[ErrorInfo(
+     kind=ErrorKind.INTERNAL,
+     message=str(e2),
+     source="app_controller._handle_click",
+     original=e2,
+    )])
+ return OK
 
 def _handle_drag(controller: 'AppController', task: dict):
  """[SDM: AppController._handle_drag]"""
@@ -1999,7 +2017,7 @@ class AppController:
           if not old_call['result']:
            old_call['result'] = output
            break
-       
+
        if kind == 'response' and 'usage' in payload:
         u = payload['usage']
         for k in ['input_tokens', 'output_tokens', 'cache_read_input_tokens', 'cache_creation_input_tokens', 'total_tokens']:
@@ -2014,7 +2032,7 @@ class AppController:
          'output': u.get('output_tokens', 0) or 0,
          'model': entry.get('model', 'unknown')
         })
-       
+
        if kind == "history_add":
         content = payload.get("content", payload.get("text", payload.get("message", "")))
         content = _resolve_log_ref(content, session_dir)
@@ -2045,7 +2063,8 @@ class AppController:
            content += f"\n\n[TOOL CALLS]\n{tc_str}"
           else:
            content = f"[TOOL CALLS]\n{tc_str}"
-         except:
+         except (TypeError, ValueError) as e:
+          logging.getLogger(__name__).debug("tool_calls json serialization failed: %s", e, extra={"source": "app_controller.cb_load_prior_log.tool_calls"})
           if content:
            content += f"\n\n[TOOL CALLS PRESENT]"
           else:
@@ -2067,9 +2086,15 @@ class AppController:
         })
       except json.JSONDecodeError:
        continue
-  except Exception as e:
+  except (OSError, IOError, json.JSONDecodeError, ValueError, TypeError, KeyError, AttributeError) as e:
+   logging.getLogger(__name__).debug("log load error: %s", e, extra={"source": "app_controller.cb_load_prior_log"})
    self.ai_status = f"log load error: {e}"
-   return
+   return Result(data=None, errors=[ErrorInfo(
+    kind=ErrorKind.INTERNAL,
+    message=str(e),
+    source="app_controller.cb_load_prior_log",
+    original=e,
+   )])
 
   self.session_usage = new_usage
   self.mma_tier_usage = new_mma_usage
@@ -2080,7 +2105,8 @@ class AppController:
     first_ts = new_token_history[0]['time']
     dt = datetime.datetime.strptime(first_ts, '%Y-%m-%dT%H:%M:%S')
     self._session_start_time = dt.timestamp()
-   except:
+   except (ValueError, TypeError, KeyError, IndexError) as e:
+    logging.getLogger(__name__).debug("token_history first_ts parse failed: %s", e, extra={"source": "app_controller.cb_load_prior_log.token_history"})
     self._session_start_time = time.time()
   self.prior_session_entries = entries
   self.prior_disc_entries = disc_entries