refactor(src): warmup.py Phase 11.3.1 - FULL Result[T] migration (5 sites)

Phase 11.3.1 (REJECT Phase 10's sliming). Per the user's explicit
direction: every try/except site that can fail MUST return Result[T].
No 'user callback' excuse; the user callbacks in WarmupManager are
Callable[[dict], None] and stay as-is. The MANAGER's INTERNAL methods
return Result[T].

Changes:
- on_complete() returns Result[bool]; fires callback via _fire_callback
  helper that captures user-callback exceptions as ErrorInfo.
- _record_success() returns Result[bool]; aggregates per-callback errors.
- _record_failure() returns Result[bool]; same pattern.
- _log_canary() returns Result[None]; uses _log_stderr helper.
- _log_summary() returns Result[None]; uses _log_stderr helper.
- _warmup_one() (io_pool callback) returns Result[bool]; delegates to
  _record_success/_record_failure.
- _log_stderr() (new helper) returns Result[None]; captures OSError.
- _fire_callback() (new helper) returns Result[bool]; captures
  user-callback exceptions.

Audit post-migration:
- L319 (_log_stderr) = INTERNAL_COMPLIANT (Heuristic A) ✓
- L337 (_fire_callback) = INTERNAL_COMPLIANT (Heuristic A) ✓
- L185 (_warmup_one) = INTERNAL_BROAD_CATCH (known limitation:
  indirect return via 'return self._record_failure(...)' is not
  detected by Heuristic A which matches 'return Result(...)' directly)
- L96 (submit raise RuntimeError) = INTERNAL_RETHROW (programmer
  error, not a runtime failure; acceptable)

Tests: 16/16 pass (test_api_hooks_warmup.py, test_gui_warmup_indicator.py).

Per conductor/tracks/result_migration_small_files_20260617/plan.md
section 11.3.1.

src/warmup.py

@@ -11,7 +11,7 @@ Public API on the manager (and exposed on AppController via delegation):
   mgr.status() - {pending, completed, failed}
   mgr.is_done() - bool
   mgr.wait(timeout) - block until done
-  mgr.on_complete(callback) - register completion callback
+  mgr.on_complete(callback) - register completion callback (returns Result[bool])
   mgr.canaries() - list[dict] of per-module canary records (observability)
   mgr.reset() - clear state (for re-warmup, e.g. in tests)
 
@@ -26,6 +26,15 @@ Canary records (one per submitted module) carry:
   elapsed_ms:  (end_ts - start_ts) * 1000
   status:      "running" | "completed" | "failed" | "cancelled"
   error:       error message string if status == "failed", else None
+
+Phase 11.3.1 (2026-06-17): FULL Result[T] migration. Every method that
+can fail returns `Result[T]` with structured `ErrorInfo`. User callbacks
+remain `Callable[[dict], None]` (the convention says external callbacks
+cannot be Result-typed); the MANAGER wraps each user-callback fire and
+returns `Result[bool]` indicating whether all callbacks succeeded.
+io_pool completion handler threads the Result through. Reference
+implementation: src/hot_reloader.py:reload()/reload_all() and
+src/hot_reloader.py's io_pool wiring.
 """
 
 import importlib
@@ -35,6 +44,8 @@ import time
 from concurrent.futures import Future, ThreadPoolExecutor
 from typing import Callable, Optional
 
+from src.result_types import ErrorInfo, ErrorKind, Result
+
 
 CompletionCallback = Callable[[dict], None]
 
@@ -125,19 +136,18 @@ class WarmupManager:
  def wait(self, timeout: Optional[float] = None) -> bool:
   return self._done_event.wait(timeout=timeout)
 
- def on_complete(self, callback: CompletionCallback) -> None:
+ def on_complete(self, callback: CompletionCallback) -> Result[bool]:
   fire_now = False
+  snap: Optional[dict] = None
   with self._lock:
    if self._done_event.is_set():
     fire_now = True
     snap = self._snapshot()
    else:
     self._callbacks.append(callback)
-  if fire_now:
-   try:
-    callback(snap)
-   except Exception as e:
-    sys.stderr.write(f"[WarmupManager] on_complete callback raised: {e}\n")
+  if fire_now and snap is not None:
+   return self._fire_callback(callback, snap, "on_complete")
+  return Result(data=True)
 
  def reset(self) -> None:
   with self._lock:
@@ -157,7 +167,7 @@ class WarmupManager:
      if c.get("start_ts") and c["elapsed_ms"] is None:
       c["elapsed_ms"] = (c["end_ts"] - c["start_ts"]) * 1000
 
- def _warmup_one(self, name: str) -> None:
+ def _warmup_one(self, name: str) -> Result[bool]:
   start_ts = time.time()
   thread = threading.current_thread()
   thread_name = thread.name
@@ -174,12 +184,11 @@ class WarmupManager:
    importlib.import_module(name)
   except BaseException as e:
    end_ts = time.time()
-   self._record_failure(name, e, end_ts)
-  else:
-   end_ts = time.time()
-   self._record_success(name, end_ts)
+   return self._record_failure(name, e, end_ts)
+  end_ts = time.time()
+  return self._record_success(name, end_ts)
 
- def _record_success(self, name: str, end_ts: Optional[float] = None) -> None:
+ def _record_success(self, name: str, end_ts: Optional[float] = None) -> Result[bool]:
   if end_ts is None: end_ts = time.time()
   callbacks: list[CompletionCallback] = []
   canary_snapshot: Optional[dict] = None
@@ -209,15 +218,16 @@ class WarmupManager:
    self._log_canary(canary_snapshot)
   if all_done:
    self._log_summary()
+  cb_errors: list[ErrorInfo] = []
   for cb in callbacks:
-   try:
-    cb(self._snapshot())
-   except Exception as e:
-    sys.stderr.write(f"[WarmupManager] _record_success callback raised: {e}\n")
+   cb_result = self._fire_callback(cb, self._snapshot(), "_record_success")
+   if not cb_result.ok:
+    cb_errors.extend(cb_result.errors)
   if all_done:
    self._done_event.set()
+  return Result(data=len(cb_errors) == 0, errors=cb_errors)
 
- def _record_failure(self, name: str, _err: BaseException, end_ts: Optional[float] = None) -> None:
+ def _record_failure(self, name: str, _err: BaseException, end_ts: Optional[float] = None) -> Result[bool]:
   if end_ts is None: end_ts = time.time()
   callbacks: list[CompletionCallback] = []
   canary_snapshot: Optional[dict] = None
@@ -243,16 +253,17 @@ class WarmupManager:
    self._log_canary(canary_snapshot)
   if all_done:
    self._log_summary()
+  cb_errors: list[ErrorInfo] = []
   for cb in callbacks:
-   try:
-    cb(self._snapshot())
-   except Exception as e:
-    sys.stderr.write(f"[WarmupManager] _record_failure callback raised: {e}\n")
+   cb_result = self._fire_callback(cb, self._snapshot(), "_record_failure")
+   if not cb_result.ok:
+    cb_errors.extend(cb_result.errors)
   if all_done:
    self._done_event.set()
+  return Result(data=len(cb_errors) == 0, errors=cb_errors)
 
- def _log_canary(self, canary: dict) -> None:
-  if not self._log_to_stderr: return
+ def _log_canary(self, canary: dict) -> Result[None]:
+  if not self._log_to_stderr: return Result(data=None)
   cid = canary["canary_id"]
   module = canary["module"]
   thread_name = canary.get("thread_name") or "?"
@@ -270,17 +281,13 @@ class WarmupManager:
     line = f"[warmup {cid}] FAILED {module} on {thread_name} (id={thread_id}): {err}{main_tag}\n"
    else:
     line = f"[warmup {cid}] {status.upper()} {module} on {thread_name} (id={thread_id}){main_tag}\n"
-   try:
-    sys.stderr.write(line)
-    sys.stderr.flush()
-   except OSError as e:
-    sys.stderr.write(f"[WarmupManager] canary log write failed: {e}\n")
+   return self._log_stderr(line, source="warmup._log_canary")
 
- def _log_summary(self) -> None:
-  if not self._log_to_stderr: return
+ def _log_summary(self) -> Result[None]:
+  if not self._log_to_stderr: return Result(data=None)
   with self._lock:
    canaries = list(self._canaries)
-  if not canaries: return
+  if not canaries: return Result(data=None)
   total = len(canaries)
   completed = sum(1 for c in canaries if c["status"] == "completed")
   failed = sum(1 for c in canaries if c["status"] == "failed")
@@ -293,17 +300,60 @@ class WarmupManager:
   if failed: parts.append(f"{failed} failed")
   if cancelled: parts.append(f"{cancelled} cancelled")
   with self._log_lock:
-    try:
-     sys.stderr.write(f"[warmup done] {total} modules: {', '.join(parts)} (sum of per-module elapsed: {total_ms:.1f}ms)\n")
-     if main_thread_violations:
-      sys.stderr.write(f"[warmup WARNING] {len(main_thread_violations)} module(s) loaded on the MAIN THREAD (violates main thread purity invariant): {', '.join(main_thread_violations)}\n")
-     sys.stderr.flush()
-    except OSError as e:
-     sys.stderr.write(f"[WarmupManager] summary log write failed: {e}\n")
+    main_line = ""
+    if main_thread_violations:
+     main_line = f"[warmup WARNING] {len(main_thread_violations)} module(s) loaded on the MAIN THREAD (violates main thread purity invariant): {', '.join(main_thread_violations)}\n"
+    summary_line = f"[warmup done] {total} modules: {', '.join(parts)} (sum of per-module elapsed: {total_ms:.1f}ms)\n"
+    r1 = self._log_stderr(summary_line, source="warmup._log_summary")
+    if main_line:
+     r2 = self._log_stderr(main_line, source="warmup._log_summary")
+     return r1 if not r1.ok else r1.with_errors(r2.errors)
+    return r1
+
+ def _log_stderr(self, line: str, source: str) -> Result[None]:
+  """Best-effort stderr write. Returns Result[None]; caller decides what to do."""
+  try:
+   sys.stderr.write(line)
+   sys.stderr.flush()
+   return Result(data=None)
+  except OSError as e:
+   return Result(data=None, errors=[ErrorInfo(
+    kind=ErrorKind.INTERNAL,
+    message=f"stderr write failed: {e}",
+    source=source,
+    original=e,
+   )])
+
+ def _fire_callback(self, cb: CompletionCallback, snap: dict, source: str) -> Result[bool]:
+  """Fire a user callback and capture any exception as Result[bool].
+
+  The user callback signature is `Callable[[dict], None]` (per the public API).
+  If it raises, we convert to ErrorInfo and best-effort log to stderr; the
+  Result captures the failure so the manager can thread it.
+  """
+  try:
+   cb(snap)
+   return Result(data=True)
+  except Exception as e:
+   err_msg = f"[WarmupManager] {source} callback raised: {e}"
+   log_result = self._log_stderr(err_msg + "\n", source=f"warmup.{source}")
+   if not log_result.ok:
+    return Result(data=False, errors=[ErrorInfo(
+     kind=ErrorKind.INTERNAL,
+     message=f"{source} callback raised: {e}; log also failed: {log_result.errors[0].message}",
+     source=f"warmup.{source}",
+     original=e,
+    )])
+   return Result(data=False, errors=[ErrorInfo(
+    kind=ErrorKind.INTERNAL,
+    message=f"{source} callback raised: {e}",
+    source=f"warmup.{source}",
+    original=e,
+   )])
 
  def _snapshot(self) -> dict[str, list[str]]:
   return {
    "pending": list(self._pending),
    "completed": list(self._completed),
    "failed": list(self._failed),
-  }
+  }