Steps 266-268: Phase 10a — semantic annotation core + sidecar persistence (32/32 tests)

Step 266: 5 semantic annotation AST types (Intent, Complexity, Risk,
Contract, SemanticTag) with JSON roundtrip and compact AST integration.
Step 267: Sidecar AST persistence (.whetstone/<file>.ast.json) with
save/load/list RPC methods, MCP tools, and permission enforcement.
Step 268: Phase 10a integration tests — multi-file sidecar workflow,
all 5 types in compact view, idempotent roundtrip, source isolation.

Also includes Sprint 10 plan, GUI/installer polish, and Emacs integration fixes.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

editor/src/panels/BottomPanel.h

@@ -56,10 +56,16 @@ static void renderBottomPanel(EditorState& state) {
         ImGui::SetNextWindowFocus();
         state.ui.focusTarget = FocusRegion::None;
     }
+    if (state.ui.requestBottomCollapse) {
+        ImGui::SetNextWindowCollapsed(true, ImGuiCond_Always);
+    }
     // ---------------------------------------------------------------
     //  Bottom panel — Output / AST / Highlighted Preview / Terminal
     // ---------------------------------------------------------------
     ImGui::Begin("Panel");
+    if (state.ui.requestBottomCollapse) {
+        state.ui.requestBottomCollapse = false;
+    }
     if (ImGui::IsWindowFocused(ImGuiFocusedFlags_RootAndChildWindows)) {
         state.ui.focusedRegion = FocusRegion::Bottom;
     }

editor/src/panels/DialogPanels.h

@@ -338,7 +338,7 @@ static void renderCommandPalette(EditorState& state) {
                 bool selected = (displayIndex == state.commandSelected);
                 std::string rowId = "##cmd_recent_" + std::to_string(displayIndex);
                 if (ImGui::Selectable(rowId.c_str(), selected,
-                                      ImGuiSelectableFlags_SpanAvailWidth,
+                                      0,
                                       ImVec2(0.0f, ImGui::GetTextLineHeightWithSpacing()))) {
                     state.commandSelected = displayIndex;
                     accept = true;
@@ -375,7 +375,7 @@ static void renderCommandPalette(EditorState& state) {
                 bool selected = (displayIndex == state.commandSelected);
                 std::string rowId = "##cmd_" + std::to_string(displayIndex);
                 if (ImGui::Selectable(rowId.c_str(), selected,
-                                      ImGuiSelectableFlags_SpanAvailWidth,
+                                      0,
                                       ImVec2(0.0f, ImGui::GetTextLineHeightWithSpacing()))) {
                     state.commandSelected = displayIndex;
                     accept = true;
@@ -502,7 +502,7 @@ static void renderCommandPalette(EditorState& state) {
             bool selected = (i == state.commandSelected);
             std::string rowId = "##file_" + std::to_string(i);
             if (ImGui::Selectable(rowId.c_str(), selected,
-                                  ImGuiSelectableFlags_SpanAvailWidth,
+                                  0,
                                   ImVec2(0.0f, ImGui::GetTextLineHeightWithSpacing()))) {
                 state.commandSelected = i;
                 accept = true;

editor/src/panels/ExplorerPanel.h

@@ -29,6 +29,18 @@ static void renderExplorerPanel(EditorState& state) {
     state.refreshFileTree();
     if (state.fileTreeRoot.path.empty()) {
         ImGui::TextDisabled("(no workspace)");
+        ImGui::Spacing();
+        ImGui::TextWrapped("Open a folder to browse project files.");
+        if (ImGui::Button("Open Folder")) {
+            auto path = FileDialog::openFolder({"Open Folder", state.workspaceRoot});
+            if (!path.empty()) {
+                state.workspaceRoot = path;
+                state.fileTreeDirty = true;
+                state.search.projectSearch.setRoot(state.workspaceRoot);
+                state.lastDialogPath = path;
+                state.refreshBuildSystem();
+            }
+        }
     } else {
         RenderFileTree(state.fileTreeRoot, state);
     }

editor/src/panels/MenuBarPanel.h

@@ -131,6 +131,10 @@ static void renderMenuBar(EditorState& state) {
                 state.ui.layoutPreset = LayoutPreset::Emacs;
             if (ImGui::MenuItem("JetBrains", nullptr, state.ui.layoutPreset == LayoutPreset::JetBrains))
                 state.ui.layoutPreset = LayoutPreset::JetBrains;
+            ImGui::Separator();
+            if (ImGui::MenuItem("Reset Layout")) {
+                state.ui.requestLayoutReset = true;
+            }
             ImGui::EndMenu();
         }
         ImGui::EndMenu();

editor/src/panels/StatusBarPanel.h

@@ -93,7 +93,7 @@ static void renderStatusBar(EditorState& state) {
 
     // Left cluster: mode, language, encoding, line ending
     std::string modeLabel = state.active()
-        ? (state.active()->bufferMode == BufferManager::BufferMode::Text ? "Text" : "Structured")
+        ? (state.active()->bufferMode == BufferManager::BufferMode::Text ? "Text Mode" : "Structured Mode")
         : "-";
     if (ImGui::Button(modeLabel.c_str())) {
         toggleBufferMode(state);