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/TextEditor.tsx

@@ -7,7 +7,11 @@
  * so this component never fetches or dispatches — it only edits.
  *
  * The toolbar (mode toggle / dirty dot / save / status) renders as its own
- * row below the host's title bar, VSCode-style.
+ * row below the host's title bar, VSCode-style — unless the host passes
+ * `toolbar: 'host'` (the merged editor-explorer mode), in which case this
+ * component skips the row and reports state + registers commands through
+ * the FileViewerProps toolbar callbacks so the host's path-input header
+ * renders the controls instead.
  */
 import { useEffect, useRef, useState } from 'react'
 import { createPortal } from 'react-dom'
@@ -24,7 +28,7 @@ import { SandboxStatusBar } from './SandboxStatusBar.tsx'
 import { appendToDraft } from './conversation-draft.ts'
 import { buildSelectionInsert, linesOfSelection } from './selection-payload.ts'
 import { t } from './locales.ts'
-import type { FileViewerProps } from './service.ts'
+import type { EditorToolbarState, FileViewerProps } from './service.ts'
 import css from './sidebar.module.css'
 
 /** Previewable files (rendered output vs source editing). */
@@ -278,8 +282,31 @@ export function TextEditor(props: FileViewerProps) {
   const [localUnlock, setLocalUnlock] = useState(() => props.store?.getPrefs().htmlViewerDefaultUnsafe === true)
   const htmlNoSandbox = props.store?.getPrefs().htmlViewerNoSandbox === true || localUnlock
 
+  // Host-toolbar mode (the merged editor header renders the controls): skip
+  // the own toolbar row, report the state after every relevant render (the
+  // JSON key guards redundant calls), and register the commands on mount.
+  const hostToolbar = props.toolbar === 'host'
+  const lastToolbarRef = useRef('')
+  useEffect(() => {
+    if (!hostToolbar) return
+    const state: EditorToolbarState = { modes: markdown || html, mode, dirty, editable, saveState }
+    const key = JSON.stringify(state)
+    if (lastToolbarRef.current === key) return
+    lastToolbarRef.current = key
+    props.onToolbarState?.(state)
+  })
+  useEffect(() => {
+    if (!hostToolbar) return
+    // `save` reads live refs only, and `setMode` is the stable state setter —
+    // registering this render's closures is safe for the mount's lifetime.
+    props.onToolbarControls?.({ setMode, save })
+    return () => { props.onToolbarControls?.(null) }
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, [hostToolbar])
+
   return (
     <>
+      {!hostToolbar && (
       <div className={css.editorHeader}>
         {(markdown || html) && (
           <div className={css.editorModeToggle}>
@@ -313,6 +340,7 @@ export function TextEditor(props: FileViewerProps) {
         )}
         {saveLabel !== '' && <span className={clsx(css.editorStatus, saveState === 'failed' && css.editorStatusError)}>{saveLabel}</span>}
       </div>
+      )}
       {editable && (
         <>
           {truncated === true && mode === 'edit' && <div className={css.editorBanner}>{t('truncation')}</div>}