UI fixes, ZTools-PartDesign merge, Silo enhancements, and BOM integration

Stylesheet fixes (KindredCreate theme):
- Add tree branch expand/collapse SVG indicators (branch_closed.svg,
  branch_open.svg) visible on dark background
- Add QSS rules for QTreeView::branch pseudo-states
- Add min-height: 20px to QHeaderView::section to fix bottom clipping
- Merge QDockWidget::title and QSint--ActionGroup QToolButton padding
  improvements from Stylesheets copy into canonical
- Add SpreadsheetGui--SheetTableView QLineEdit cell editor styling
- Sync all three QSS copies (resources/preferences, src/Gui/Stylesheets,
  src/Gui/PreferencePacks) to canonical version

ZTools-PartDesign workbench integration:
- Add _ZToolsPartDesignManipulator via WorkbenchManipulator API
- Injects DatumCreator, DatumManager into Part Design Helper Features toolbar
- Injects EnhancedPocket into Part Design Modeling Features toolbar
- Injects RotatedLinearPattern into Part Design Transformation Features toolbar
- Adds corresponding PartDesign menu entries after PartDesign_Boolean

Silo enhancements:
- Add Silo_ToggleMode command: toggle switch in File toolbar that swaps
  Ctrl+O/S/N between standard FreeCAD and Silo equivalents
- Add SSL certificate file browser in Silo Settings dialog (SslCertPath
  preference, supports .pem/.crt/.cer)
- Update _get_ssl_context() to load custom CA cert before system CAs
- Expand SiloMenuManipulator: Silo_New, Silo_Open, Silo_Save, Silo_Commit,
  Silo_Pull, Silo_Push, Silo_BOM in File menu
- Integrate upstream Silo_BOM command (tabbed BOM/Where-Used dialog)

Submodule updates:
- silo: Silo mode toggle, SSL cert browsing, BOM menu integration
- ztools: PartDesign WorkbenchManipulator and Catppuccin theme sync

Documentation:
- Add docs/REPOSITORY_STATE.md: comprehensive repository state report with
  architecture overview, submodule status, potential issues, feature stubs,
  and Silo integration path forward

resources/preferences/KindredCreate/KindredCreate.qss

@@ -247,8 +247,9 @@ QDockWidget {
 QDockWidget::title {
     background-color: #181825;
     color: #cdd6f4;
-    padding: 6px;
+    padding: 8px 6px;
     border-bottom: 1px solid #313244;
+    min-height: 18px;
 }
 
 QDockWidget::close-button,
@@ -786,6 +787,16 @@ QTreeView::branch:selected {
     background-color: #45475a;
 }
 
+QTreeView::branch:has-children:!has-siblings:closed,
+QTreeView::branch:closed:has-children:has-siblings {
+    image: url(qss:images_dark-light/branch_closed.svg);
+}
+
+QTreeView::branch:open:has-children:!has-siblings,
+QTreeView::branch:open:has-children:has-siblings {
+    image: url(qss:images_dark-light/branch_open.svg);
+}
+
 /* =============================================================================
    List View
    ============================================================================= */
@@ -859,6 +870,7 @@ QHeaderView::section {
     border-right: 1px solid #45475a;
     border-bottom: 1px solid #45475a;
     padding: 6px 8px;
+    min-height: 20px;
 }
 
 QHeaderView::section:hover {
@@ -1138,7 +1150,8 @@ QSint--ActionGroup QToolButton {
     color: #cdd6f4;
     border: none;
     border-radius: 4px;
-    padding: 6px;
+    padding: 8px 6px;
+    min-height: 18px;
 }
 
 QSint--ActionGroup QToolButton:hover {
@@ -1186,6 +1199,16 @@ SpreadsheetGui--SheetTableView QHeaderView::section {
     padding: 4px;
 }
 
+/* Spreadsheet cell editor - reduce padding for better text visibility */
+SpreadsheetGui--SheetTableView QLineEdit {
+    background-color: #313244;
+    color: #cdd6f4;
+    border: 1px solid #cba6f7;
+    border-radius: 0px;
+    padding: 1px 2px;
+    margin: 0px;
+}
+
 /* Python Console */
 Gui--PythonConsole {
     background-color: #11111b;