feat(modal): Add patch approval modal manager

- Create src/patch_modal.py with PatchModalManager class
- Manage patch approval workflow: request, apply, reject
- Provide singleton access via get_patch_modal_manager()
- Add 8 unit tests for modal manager

src/patch_modal.py

@@ -0,0 +1,73 @@
+from typing import Optional, Callable, List
+from dataclasses import dataclass, field
+
+@dataclass
+class PendingPatch:
+  patch_text: str
+  file_paths: List[str]
+  generated_by: str
+  timestamp: float
+
+class PatchModalManager:
+  def __init__(self):
+    self._pending_patch: Optional[PendingPatch] = None
+    self._show_modal: bool = False
+    self._on_apply_callback: Optional[Callable[[str], bool]] = None
+    self._on_reject_callback: Optional[Callable[[], None]] = None
+  
+  def request_patch_approval(self, patch_text: str, file_paths: List[str], generated_by: str = "Tier 4 QA") -> bool:
+    from time import time
+    self._pending_patch = PendingPatch(
+      patch_text=patch_text,
+      file_paths=file_paths,
+      generated_by=generated_by,
+      timestamp=time()
+    )
+    self._show_modal = True
+    return True
+  
+  def get_pending_patch(self) -> Optional[PendingPatch]:
+    return self._pending_patch
+  
+  def is_modal_shown(self) -> bool:
+    return self._show_modal
+  
+  def set_apply_callback(self, callback: Callable[[str], bool]) -> None:
+    self._on_apply_callback = callback
+  
+  def set_reject_callback(self, callback: Callable[[], None]) -> None:
+    self._on_reject_callback = callback
+  
+  def apply_patch(self, patch_text: str) -> bool:
+    if self._on_apply_callback:
+      return self._on_apply_callback(patch_text)
+    return False
+  
+  def reject_patch(self) -> None:
+    self._pending_patch = None
+    self._show_modal = False
+    if self._on_reject_callback:
+      self._on_reject_callback()
+  
+  def close_modal(self) -> None:
+    self._show_modal = False
+  
+  def reset(self) -> None:
+    self._pending_patch = None
+    self._show_modal = False
+    self._on_apply_callback = None
+    self._on_reject_callback = None
+
+_patch_modal_manager: Optional[PatchModalManager] = None
+
+def get_patch_modal_manager() -> PatchModalManager:
+  global _patch_modal_manager
+  if _patch_modal_manager is None:
+    _patch_modal_manager = PatchModalManager()
+  return _patch_modal_manager
+
+def reset_patch_modal_manager() -> None:
+  global _patch_modal_manager
+  if _patch_modal_manager:
+    _patch_modal_manager.reset()
+  _patch_modal_manager = None