feat(editor): 文件窗口与资源管理器二合一 + 声明式设置 select 行 (#151)

* feat(editor): merged explorer mode — path input, docked file tree, global name search

New editorExplorer pref (default on, editor card gear): the editor tab gains
a path-input header and a toggleable right-docked tree panel (per-tab state
in tab.meta.treeOpen; file tabs default closed, the seeded path-less home
tab defaults open). Fresh sessions seed that empty editor tab instead of
the explorer tab when merged mode is on; the standalone explorer tab stays
in the + menu unchanged.

- Extract FileTree.tsx from ExplorerView (shared by both hosts)
- Host fs.search route: recursive case-insensitive name search rooted at
  the session cwd, budget-capped (200 matches / 100k visited), skips .git,
  never descends symlink dirs
- EditorHost reads the pref reactively (boolean snapshot) and keeps the
  pre-merge layout verbatim when off

* feat(settings): select row type for declarative settings; editorExplorer as iconed select

- SidebarSettingToggle gains type 'select' with options {value,title,desc,icon}
  and multi (default false; stores the picked values as an array in options
  order). Any option carrying an icon renders big-icon option cards in the
  dropdown and the icon in the closed anchor; icon-less rows are one-line text.
- SelectRow in SideCardSection rides the primitives Menu (portal); single-pick
  commits and closes, multi toggles and stays open. Wired for both host-prefs
  toggles and plugin-owned pluginToggles via the new onSelectValue seam.
- The editorExplorer merged-mode pref is now an iconed select (merged vs
  separate) instead of a switch; the stored value stays boolean.
- Advertise the capability as 'settingSelect' in SIDEBAR_FEATURES.

* feat(editor): unify explorer into the editor surface, resizable tree dock, hoisted toolbar

- One tree implementation, two presentations: the shared TreePanel (global
  name search + refresh + FileTree) docks as the editor tab's right panel
  and — in merged mode — fills the explorer tab's window; the pref-off
  explorer keeps its legacy header shell.
- The docked panel drag-resizes from its left edge (160-480px clamp),
  persisted as tab.meta.treeWidth alongside treeOpen.
- The text editor's preview/edit/save toolbar moves into the path-input
  header row: FileViewerProps gains internal toolbar fields ('host' mode
  skips the viewer's own row, reports EditorToolbarState and registers
  EditorToolbarControls); non-merged mode is byte-identical to before.

* feat(editor): single files window with in-place switching; explorer descriptor removed

- editor tab replaces explorer on the + menu (order 10, Files); persisted
  explorer tabs migrate to the editor home tab via sanitizeState
- editorExplorer now only controls open behavior: merged = in-place
  updateTab, independent = openSidebarFile; both modes share the merged
  chrome (path input + hoisted preview/edit/save toolbar + tree toggle)
- file tree context menu gains 'open in new tab' / 'open to the side'
  (mintTabId avoids the id safety net; insertLeafAt splits right)
- tree dock resize uses pointer capture (touch-action none, 6px handle)
- defaults: openByDefault off, sidebar width 35%
- file tree clips horizontal overflow (no sideways scroll)
- e2e: mount lane arms the editor-chunk wait before goto and clicks the
  tree row's left edge (hover @-reference button sits mid-row); drag lane
  expands the panel first (collapsed push writes 0px), waits for the
  slide-in to settle, and picks the leftmost col-resize strip; 'Files'
  title assertions require draggable to skip the bottom panel's welcome
  cards

* feat(editor): split mode turns the path-less window into the standalone explorer

In independent (split) mode a path-less files window renders ONLY the
tree panel (search + FileTree, full-window form) — no path input, no
hoisted toolbar, no tree toggle. File clicks open per-path editor tabs
(full chrome, tree docked closed by default) through openSidebarFile,
unchanged. Merged mode is untouched (chrome + docked tree, in-place
switching). TreePanel's previously reserved 'full' prop now has its
consumer.

src/client/sidebar.module.css

@@ -666,6 +666,8 @@
   flex: 1;
   min-height: 0;
   overflow-y: auto;
+  /* Deep trees truncate their labels instead of scrolling horizontally. */
+  overflow-x: hidden;
   padding: 2px 6px 8px;
 }
 
@@ -677,7 +679,12 @@
   display: flex;
   align-items: center;
   gap: 6px;
+  /* border-box keeps the inline indent padding (depth * 22 + 6) INSIDE the
+     row's 100% width — without it deep rows overflow and force a horizontal
+     scrollbar on the tree body. */
+  box-sizing: border-box;
   width: 100%;
+  max-width: 100%;
   height: 34px;
   padding: 0 8px;
   border: none;
@@ -716,8 +723,12 @@
 }
 
 .explorerName {
+  /* min-width: 0 lets the flex item shrink below its content so the label
+     truncates with an ellipsis instead of widening the row. */
+  min-width: 0;
   overflow: hidden;
   text-overflow: ellipsis;
+  white-space: nowrap;
 }
 
 /* The hover-revealed @-reference button at the row's far right (and the
@@ -799,6 +810,139 @@
   white-space: nowrap;
 }
 
+/* Merged mode (the editorExplorer pref): the header's path input replaces
+   the plain title, and a toggleable file tree docks at the tab's right edge. */
+.editorPathInput {
+  flex: 1;
+  min-width: 0;
+  height: 28px;
+  padding: 0 10px;
+  border: 1px solid var(--dsw-alias-border-l1);
+  border-radius: 6px;
+  background: var(--dsw-alias-bg-layer-1);
+  color: var(--dsw-alias-label-primary);
+  font: var(--dsw-font-xxs-12);
+}
+
+.editorPathInput:focus {
+  outline: none;
+  border-color: var(--dsw-alias-border-l2);
+}
+
+/* The tree-panel toggle in the header: active = panel open (the selected
+   fill of the tab strip). */
+.editorTreeToggleActive {
+  color: var(--dsw-alias-label-primary);
+  background: var(--dsw-alias-interactive-bg-active);
+}
+
+.editorBody {
+  flex: 1;
+  min-height: 0;
+  display: flex;
+}
+
+.editorMain {
+  flex: 1;
+  min-width: 0;
+  min-height: 0;
+  display: flex;
+  flex-direction: column;
+}
+
+/* The docked file tree: the wrapper owns the (drag-adjustable) width and
+   the hairline separation; the resize handle is a wider invisible strip on
+   its left edge with a hover affordance. */
+.editorTreeDock {
+  position: relative;
+  flex: none;
+  min-height: 0;
+  display: flex;
+  border-left: 1px solid var(--dsw-alias-border-l1);
+}
+
+.editorTreeResize {
+  position: absolute;
+  top: 0;
+  bottom: 0;
+  /* Inside the dock (left edge): pointer capture on the handle keeps the
+     drag alive even when the pointer leaves the strip. */
+  left: 0;
+  width: 6px;
+  cursor: col-resize;
+  touch-action: none;
+  z-index: 3;
+}
+
+.editorTreeResize:hover {
+  background: var(--dsw-alias-border-l2);
+}
+
+.editorTreePanel {
+  flex: 1;
+  min-width: 0;
+  min-height: 0;
+  display: flex;
+  flex-direction: column;
+}
+
+/* The tree panel's full-window form (the `full` prop): fill the tab body. */
+.editorTreePanelFull {
+  flex: 1;
+}
+
+.editorTreeSearch {
+  flex: none;
+  display: flex;
+  align-items: center;
+  gap: 4px;
+  padding: 6px 8px;
+  border-bottom: 1px solid var(--dsw-alias-border-l1);
+}
+
+.editorSearchInput {
+  flex: 1;
+  min-width: 0;
+  height: 26px;
+  padding: 0 10px;
+  border: 1px solid var(--dsw-alias-border-l1);
+  border-radius: 6px;
+  background: var(--dsw-alias-bg-layer-1);
+  color: var(--dsw-alias-label-primary);
+  font: var(--dsw-font-xxs-12);
+}
+
+.editorSearchInput:focus {
+  outline: none;
+  border-color: var(--dsw-alias-border-l2);
+}
+
+.editorSearchHint {
+  padding: 8px 12px;
+  font: var(--dsw-font-xxs-12);
+  color: var(--dsw-alias-label-tertiary);
+}
+
+.editorSearchResult {
+  display: block;
+  width: 100%;
+  padding: 4px 8px;
+  border: none;
+  border-radius: 6px;
+  background: transparent;
+  color: var(--dsw-alias-label-primary);
+  font: var(--dsw-font-xxs-12);
+  text-align: left;
+  cursor: pointer;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+}
+
+.editorSearchResult:hover {
+  background: var(--dsw-alias-interactive-bg-hover);
+}
+
 .editorStatus {
   font: var(--dsw-font-xxxs-11);
   color: var(--dsw-alias-label-tertiary);