feat(ui): 文件二级页面间距规整（8px 网格）+ 浮窗默认尺寸改手机竖屏比例

- 文件页 chrome 行统一：路径行与树搜索行同为 41px 高（路径输入框改
  border-box 28px 总高）、gap 统一 6px、内边距统一 6px 8px
- 树体侧距 6→8px 对齐 chrome 行；markdown 预览 10/14→12/16（与错误
  文案块一致）；CodeMirror scroller 新增同款 12/16 内边距（预览/编辑
  切换文字位置不跳）；截断横幅 12→8px
- 浮窗默认尺寸 480×360 → 390×780（1:2 手机竖屏比例），创建时先按
  视口减 24px 钳制再居中，矮视口得到更矮的窗而非溢出
- 测试/文档同步：state/free-window 预期重算（含 clampMove 回推的
  y=24 语义）、e2e 断言宽度上界、AGENTS §7.5 与设计文档

src/client/sidebar.module.css

@@ -876,7 +876,7 @@ body[data-dsh-sidebar-dragging] .bottomPanel {
   overflow-y: auto;
   /* Deep trees truncate their labels instead of scrolling horizontally. */
   overflow-x: hidden;
-  padding: 2px 6px 8px;
+  padding: 4px 8px 8px;
 }
 
 /* One tree row: the app's session-row cell (34px, radius 8, inset, hover
@@ -1196,7 +1196,7 @@ body[data-dsh-sidebar-dragging] .bottomPanel {
   display: flex;
   align-items: center;
   gap: 6px;
-  padding: 4px 8px;
+  padding: 6px 8px;
   border-bottom: 1px solid var(--dsw-alias-border-l1);
 }
 
@@ -1215,6 +1215,7 @@ body[data-dsh-sidebar-dragging] .bottomPanel {
 .editorPathInput {
   flex: 1;
   min-width: 0;
+  box-sizing: border-box;
   height: 28px;
   padding: 0 10px;
   border: 1px solid var(--dsw-alias-border-l1);
@@ -1297,7 +1298,7 @@ body[data-dsh-sidebar-dragging] .bottomPanel {
   flex: none;
   display: flex;
   align-items: center;
-  gap: 4px;
+  gap: 6px;
   padding: 6px 8px;
   border-bottom: 1px solid var(--dsw-alias-border-l1);
 }
@@ -1430,7 +1431,7 @@ body[data-dsh-sidebar-dragging] .bottomPanel {
 
 .editorBanner {
   flex: none;
-  padding: 4px 12px;
+  padding: 4px 8px;
   font: var(--dsw-font-xxxs-11);
   color: var(--dsw-alias-state-warn-label);
   background: var(--dsw-alias-state-warn-tertiary);
@@ -1633,6 +1634,12 @@ body[data-dsh-sidebar-dragging] .bottomPanel {
   height: 100%;
 }
 
+/* Code lines get the same 12/16 inset as the markdown preview, so toggling
+   preview/edit never jumps the text's resting position. */
+.editorCm :global(.cm-scroller) {
+  padding: 12px 16px;
+}
+
 .editorCm :global(.cm-editor.cm-focused) {
   outline: none;
 }
@@ -1688,7 +1695,7 @@ body[data-dsh-sidebar-dragging] .bottomPanel {
   flex: 1;
   min-height: 0;
   overflow-y: auto;
-  padding: 10px 14px;
+  padding: 12px 16px;
   font: var(--dsw-font-xs-13);
 }
 

src/client/state.ts

@@ -120,9 +120,12 @@ export const BOTTOM_DEFAULT = 220
  *  header plus some content), the ceiling is the viewport. */
 export const FLOAT_MIN_W = 320
 export const FLOAT_MIN_H = 200
-/** Geometry a fresh free window starts with (clamped to the viewport). */
-export const FLOAT_DEFAULT_W = 480
-export const FLOAT_DEFAULT_H = 360
+/** Geometry a fresh free window starts with: a phone-like portrait ratio
+ *  (390×780 ≈ 1:2). The creation path additionally caps the size to the
+ *  viewport (minus a 24px margin), so a short viewport gets a shorter —
+ *  not overflowing — window instead of an exact ratio. */
+export const FLOAT_DEFAULT_W = 390
+export const FLOAT_DEFAULT_H = 780
 
 let nextIdCounter = 0
 /** Unique pane/tab id within one state instance. */
@@ -777,11 +780,17 @@ export function floatTab(state: SidebarState, tabId: string, x: number, y: numbe
     if (leaf.tabs.length === 0) emptied = true
   })
   if (emptied) node = removeLeafAt(node, source.id)
+  // Phone-ratio default, capped to the viewport before centering so the
+  // clamped position never leaves the window's bottom past the fold.
+  const vw = viewportW()
+  const vh = viewportH()
+  const width = Math.min(FLOAT_DEFAULT_W, Math.max(FLOAT_MIN_W, vw - 24))
+  const height = Math.min(FLOAT_DEFAULT_H, Math.max(FLOAT_MIN_H, vh - 24))
   const window = clampFloatGeometry(
-    x - FLOAT_DEFAULT_W / 2,
-    y - FLOAT_DEFAULT_H / 2,
-    FLOAT_DEFAULT_W,
-    FLOAT_DEFAULT_H,
+    x - width / 2,
+    y - height / 2,
+    width,
+    height,
   )
   const next: SidebarState = {
     ...state,