refactor(src): Phase 10.2 batch 6 - hot_reloader + warmup + startup_profiler

hot_reloader.py (1 site - module reload with broad except):
- reload() returns Result[bool] now. The migration catches the
  broad Exception, captures it as ErrorInfo with the traceback in
  last_error, and returns Result(data=False, errors=[...]).
- reload_all() returns Result[bool]; aggregates per-module errors.
- The class still tracks last_error and is_error_state for
  backwards-compat with any caller reading the class attributes.

warmup.py (5 sites):
- L139 (on_complete callback fire): was except ...: pass.
  Now logs to sys.stderr with the exception.
- L215 (_record_success callback fire): same.
- L249 (_record_failure callback fire): same.
- L276 (_log_canary stderr.write): was except OSError: pass.
  Now logs the OSError itself.
- L300 (_log_summary stderr.write): same.

startup_profiler.py (1 site - context manager):
- phase() is a context manager (yields); can't return Result.
  The except inside the finally block now logs the OSError.

Tests updated for hot_reloader to check result.ok and result.data.

Tests verified:
- tests/test_hot_reloader.py (9 tests) PASS
- tests/test_hot_reload_integration.py (13 tests) PASS
- tests/test_warmup.py (10 tests) PASS
- tests/test_warmup_canaries.py (18 tests) PASS

src/hot_reloader.py

@@ -8,6 +8,8 @@ import traceback
 from dataclasses import dataclass, field
 from typing      import Any
 
+from src.result_types import Result, ErrorInfo, ErrorKind
+
 
 @dataclass
 class HotModule:
@@ -37,11 +39,12 @@ class HotReloader:
    setattr(app, key, value)
 
  @classmethod
- def reload(cls, module_name: str, app: Any) -> bool:
+ def reload(cls, module_name: str, app: Any) -> Result[bool]:
   if module_name not in cls.HOT_MODULES:
-   cls.last_error     = f"Module {module_name} not registered"
+   err_msg = f"Module {module_name} not registered"
+   cls.last_error     = err_msg
    cls.is_error_state = True
-   return False
+   return Result(data=False, errors=[ErrorInfo(kind=ErrorKind.NOT_FOUND, message=err_msg, source=f"hot_reloader.reload[{module_name}]")])
 
   hm    = cls.HOT_MODULES[module_name]
   state = cls.capture_state(app, hm.state_keys)
@@ -54,16 +57,19 @@ class HotReloader:
     importlib.import_module(module_name)
    cls.last_error     = None
    cls.is_error_state = False
-   return True
-  except Exception:
+   return Result(data=True)
+  except Exception as e:
    cls.restore_state(app, state)
-   cls.last_error     = traceback.format_exc()
+   tb = traceback.format_exc()
+   cls.last_error     = tb
    cls.is_error_state = True
-   return False
+   return Result(data=False, errors=[ErrorInfo(kind=ErrorKind.INTERNAL, message=str(e), source=f"hot_reloader.reload[{module_name}]", original=e)])
 
  @classmethod
- def reload_all(cls, app: Any) -> bool:
-  success = True
+ def reload_all(cls, app: Any) -> Result[bool]:
+  errors: list[ErrorInfo] = []
   for name in cls.HOT_MODULES:
-   if not cls.reload(name, app): success = False
-  return success
+   result = cls.reload(name, app)
+   if not result.ok:
+    errors.extend(result.errors)
+  return Result(data=len(errors) == 0, errors=errors)