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/locales.ts

@@ -11,10 +11,25 @@
 
 /** The zh dictionary (also registered into the DSH locale registry under {@link LOCALE_NS}). */
 export const zh = {
+  files: '文件',
   explorer: '资源管理器',
   git: '源代码管理',
   terminal: '终端',
   editor: '编辑器',
+  editorExplorer: '文件打开方式',
+  editorExplorerDesc: '控制文件打开方式',
+  editorExplorerMerged: '合并',
+  editorExplorerMergedDesc: '文件在同一窗口内原地切换；新窗口默认展开文件树',
+  editorExplorerSplit: '独立',
+  editorExplorerSplitDesc: '无路径窗口即资源管理器（仅文件树）；文件各自新开窗口（带文件树，默认收起）',
+  editorTreeToggle: '文件树面板',
+  editorPathPlaceholder: '输入文件路径（相对会话目录或绝对路径），Enter 打开',
+  editorSearchPlaceholder: '按文件名搜索…',
+  editorSearchNoResults: '无匹配文件',
+  editorSearchTruncated: '结果过多，仅显示部分匹配',
+  editorEmptyHint: '从右侧文件树或上方路径输入框选择文件开始预览',
+  openFileNewTab: '在新 Tab 中打开',
+  openFileSide: '在侧边打开',
   newTab: '新建标签页',
   openExplorer: '资源管理器',
   brokenSymlink: '失效的软链接',
@@ -238,10 +253,25 @@ export const zh = {
 
 /** The en dictionary (key-set-equal to zh, enforced by the type annotation). */
 export const en: Record<keyof typeof zh, string> = {
+  files: 'Files',
   explorer: 'Explorer',
   git: 'Source Control',
   terminal: 'Terminal',
   editor: 'Editor',
+  editorExplorer: 'File open behavior',
+  editorExplorerDesc: 'Controls how files open',
+  editorExplorerMerged: 'Merged',
+  editorExplorerMergedDesc: 'Files switch in place in the same window; new windows start with the tree open',
+  editorExplorerSplit: 'Separate',
+  editorExplorerSplitDesc: 'Path-less windows are the standalone explorer (tree only); each file opens its own window (tree docked, closed by default)',
+  editorTreeToggle: 'File tree panel',
+  editorPathPlaceholder: 'File path (relative to the session directory or absolute), Enter to open',
+  editorSearchPlaceholder: 'Search files by name…',
+  editorSearchNoResults: 'No matching files',
+  editorSearchTruncated: 'Too many results — showing a partial list',
+  editorEmptyHint: 'Pick a file from the tree panel or the path input above to start previewing',
+  openFileNewTab: 'Open in New Tab',
+  openFileSide: 'Open to the Side',
   newTab: 'New tab',
   openExplorer: 'Explorer',
   brokenSymlink: 'Broken symlink',